bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Boundaries in Germanium
Authors: Wagner Richard S. , Chalmers Bruce
Published: April 2005

The relative energies and the boundary orientations of simple tilt boundaries in germanium crystals have been measured. The measurements were made on columnar tricrystals prepared by the modified Czochralski method. The orientations of the columnar tricrystals were either 〈100〉 and 〈111〉 isoxial or (100) isoplanar. The relative grain boundary energies were measured as a function of the angular misorientation θ between two grains. The crystallographic orientations of the grain boundary plane were also determined.

It was found that the relative energy of 〈100〉 and 〈111〉 tilt boundaries up to about 15° of misorientation changes with misorientation as predicted by Read and Shockley's theory. For larger angles of misorientation, the grain boundary energy is essentially independent of the angle of misorientation. This indicates a significant but continuous change in boundary structure at the transition region.

Additional evidence for the difference in the structure of low- and high-angle tilt boundaries was found in the apparent strong dependence of the energy of low-angle boundaries on the boundary orientation. Low-angle (100) twist boundaries were not observed.
Grain Boundary and Lattice Diffusion in Polycrystalline Bodies
Authors: Levine H. S. , MacCallum C. J.
Published: April 2005

Diffusion in a polycrystalline body is discussed under the assumption that two interrelated mechanisms consisting of diffusion through the grains and in the boundaries around the grains are dominant in different penetration regions. The general behavior of the average concentration-distribution of diffusant is described for the separate action of each mechanism, and the effects of their combined action are inferred. A realistic diffusion model for a polycrystalline body and a suitable empirical function to describe the loss of diffusant from the boundaries to the grains form the basis for these computations.

Results are specifically applied to the analysis of the usual sectioning technique for measuring the ratio of grain boundary to lattice diffusion constants in a polycrystalline body. It is shown that, in the penetration range most commonly covered in polycrystalline diffusion experiments, the log of the average concentration varies as the 6/5 power of penetration depth contrary to the linear law reported previously. Comparison is made between the present and previous methods for establishing the grain boundary diffusivity of silver. The results are found to differ by a factor of 3 or 4. Criteria for validity of the method associated with the relative magnitudes of reduced time, grain size, and the ratio of grain boundary to lattice diffusion constants are established. Some of the results reported for Zn and Cd do not satisfy these criteria.
Lattice Displacements by Fast Electrons
Authors: Compton W. Dale , Arnold George W.
Published: April 2005

A discussion is given of the processes by which atoms are displaced from their lattice sites by incident fast electrons. In addition to direct displacement by the incident electron, expressions are derived for the fraction of atoms displaced by fast moving atoms and by fast secondary electrons, both of which are generated initially by the incident electron. A discussion of thermal spikes is given. A thermal spike process is discussed that might lead to the generation of defects with x irradiation in materials that exhibit a threshold energy for a displacement by a charged particle.
X-Ray Examination of Brittle Fractures in Extruded Chromium
Authors: Weaver C. W. , Gross K. A.
Published: April 2005

X-ray examinations of brittle fractures in polycrystalline chromium, produced at temperatures between 193°K and 623°K, have been made. Estimates of the amount of deformation present at the fracture surfaces showed that very large plastic strains were associated with brittle cleavage fracture at the higher temperatures, such that the length of a self-sustaining crack calculated according to the modified Griffith crack formula of Hall, was more than an order greater than the mean grain diameter of the material. Plastic strains of this order would be expected to result in ductile behavior. It is suggested that brittle failure was caused by the presence of a fine dispersion of precipitate particles, which delayed the action of cross slip in sealing off the early stages of cracking. The spacing of the precipitate particles was estimated to be between 6000 and 7000 A.
Mobility of Hydrogen and Deuterium Positive Ions in their Parent Gases
Authors: Rose D. J.
Published: April 2005

The mobilities of positive ions in H2 and D2 have been measured, using a pulsed Townsend technique. For hydrogen, the mobility μ0 corrected to 0°C was 11.8 (cm2/v×sec) at E/p0=26(v/sec×mm Hg), increasing to a maximum of 15.3 at E/p0=48, then decreasing to 11.6 at E/p0=150. For deuterium, the mobility was about 0.75 the value for hydrogen throughout the range of E/p0. The experiment was performed with uranium-purified gas in an ultra-high vacuum system. Ions were not identified as atomic, diatomic, or triatomic; there was no conclusive evidence of more than one ion at any value of E/p0. The H2 mobility data are significantly lower than those attributed to Mitchell in the range 20<E/p0<40, and lower than the value ≈12.5 for zero-field mobility generally reported.
Correlation between Certain Extinction Bands of Solids and Plasma Resonance
Authors: Gossick B. R.
Published: April 2005

A correlation is reported between certain optical extinction bands in sapphire, quartz, the silver and alkali halides, and the calculated plasma resonance of electrons in colloidal particles which are either known or expected to be present. This correlation suggests not only that pile neutrons produce lithium particles in lithium fluoride, but aluminum particles in sapphire, and silicon particles in quartz.
Attenuation of the Shock Wave Produced in a Solid by a Flying Plate
Authors: Fowles G. R.
Published: April 2005

The attenuation of the plane shock wave produced in a solid by a flying plate of the same material is treated neglecting dissipative processes and effects of material rigidity. Explicit formulas for the position of the shock front and the shape of the pulse as functions of time are obtained by application of Friedrich's method. A numerical example for an aluminum target and projectile is presented to illustrate some of the features of the calculation, and an experiment is proposed to test the theory. The experiment should also allow a reasonably precise measurement of sound velocity immediately behind the shock front to be obtained. This possibility applies equally well to the case of target and projectile of different materials.
Behavior of Individual Dislocations in Strain-Hardened LiF Crystals
Authors: Gilman J. J. , Johnston W. G.
Published: April 2005

The velocities of dislocations have been measured as a function of stress for both undeformed and deformed crystals. The motion is slower at a given stress in a strained crystal, and extra stress is needed to give the same velocity in a strained crystal as in one that is unstrained. It has been found that the extra stress is just equal to the difference in macroscopic flow stresses for the two states of a crystal.

Existing theories of strain-hardening do not correctly predict the behavior of LiF. Barrier-type theories are ruled out because the distance that a dislocation can move in a strain-hardened crystal does not seem to be limited. Theories of Taylor hardening or of cutting of a dislocation forest do not give the observed dependence of strain-hardening on dislocation density. It is observed that the strain-hardening increment is proportional to the dislocation density (also to the plastic strain), and the proportionality constant is 3–5 dynes/disl. The data are consistent with the idea that the hardening is due to defects left in the wakes of moving dislocations. These defects would interfere with the movement of subsequent dislocations on the same or nearby glide planes.
Piezoresistive Effect in p Type PbTe
Authors: Hollander Lewis E. , Diesel T. J.
Published: April 2005

A large positive piezoresistive effect has been observed in p type PbTe. The following room temperature coefficients were determined: πHydrostatic=+150±50; π11=80±30; π[111]=+220±50, all in 10−12/d. The shear coefficient π44 is estimated to be +255×10−12 cm2/d. The calculated value of π12 was +35±40×10−12 cm2/d. These measurements were performed on single-crystal, p type PbTe with a mobility of approximately 700 cm2/v sec and a carrier concentration of about 1018 per cm3. Consideration of the coefficients indicates the major axes of the energy ellipsoids are oriented in the [111] direction, which is in agreement with magnetoresistance measurements.
Molecular Trajectories in Electric Fields and State Selection in a Beam of Sodium Chloride
Authors: Peter M. , Venkates H. G. R. , Strandberg M. W. P.
Published: April 2005

A molecular beam of sodium chloride can be partially sorted with respect to the rotational levels of the molecule when it is passed through an inhomogeneous electric field. The possibility of state selection of the beam in one of the lower rotational states of the molecule (J=2; |M| =0, 1, 2) has been investigated by studying the molecular trajectories for the rotational states J=1; |M| =1, 0 and J=2; |M| =2, 1, 0. A typical calculation for a state selector is given.
Polyhedral Holes in Evaporated AuCu Films
Authors: Phillips Victor A.
Published: April 2005

A transmission electron microscope study of ordered (001) films of Au-50 at. % Cu made by evaporation in vacuo onto cleaved rocksalt at 400°C showed (a) the presence of a 6 sided roughly hexagonal single crystal area in the film about 2 μ across apparently surrounded by polycrystals, the 3 pairs of sides being nearly parallel to [1̄00],[1̄20], and [1̄1̄0], respectively, (b) streaks within this crystal interpretable as twins on (111), (c) holes through the film tended within this crystal to be polyhedral, developing sides parallel to 〈100〉 and 〈110〉. The latter observation indicates that the effective supersaturation during evaporation is relatively low.
Production and Demonstration of Atomically Clean Metal Surfaces
Authors: Hagstrum H. D. , D'Amico C.
Published: April 2005

Ion bombardment as a means of cleaning solid surfaces has been tested by applying it to the metal tungsten. The test, which showed the resulting surface to be clean, is a sensitive one because atomically clean tungsten is very reactive to the common gases. The test is definitive since it is performed on a material for which there is overwhelming evidence that another means, namely heating, does produce an atomically clean surface. The phenomenon used in this work to observe surface conditions during the cleaning procedures is the Auger-type ejection of electrons by slowly moving positive ions. This is again shown to be a sensitive means of detecting surface contamination. Data on the electron release by ions from heavily contaminated metal surfaces are reported.
Influence of Transverse Modes on Photoconductive Decay in Filaments
Authors: Blakemore J. S. , Nomura K. C.
Published: April 2005

The roles of high order modes are discussed for the decay of excess carriers in a semiconducting filament. A general solution is given for the strength of the various modes when excess generation (i.e., illumination) is any function of time and space. Solutions for several specific cases are illustrated in graphical and tabular form. It is well known from the discussions of Shockley and of Stevenson and Keyes that odd-numbered modes can augment the surface recombination of the fundamental mode: the present calculations show that for typical generative procedures this increased recombination is considerably more serous than has been generally supposed. The role is noted of even numbered (antisymmetric) modes, which contribute nothing to filament photoconductance, but which arise under antisymmetric generation conditions to describe transverse diffusion (and usually to disturb the relative amplitudes of the odd modes). Attention is drawn to the fact that some odd modes can have a generative behavior when carrier creation is a suitable function of position. This is turned to advantage in suggesting how lifetime may be measured in a filament with minimum interference from the surface.
Optical Constants of Germanium in the Region 0–10 ev
Authors: Rimmer M. P. , Dexter D. L.
Published: April 2005

A program has been written for the IBM 650 Digital Computer to evaluate the Kramers-Kronig dispersion relation between real and imaginary parts of the index of refraction, n and k. By this means measurement of the reflection coefficient over a sizable energy range allows the determination of n and k throughout most of this region. Reflection data of Philipp and Taft on germanium have been analyzed in this way, and the results are compared with those of Philipp and Taft obtained by another method. The results are similar, minor differences occurring in the fine structure. The computer program is available on request.
Intensities of λ1850 and λ2537 in Low-Pressure Mercury Vapor Lamps with Rare Gas Present
Authors: Barnes Bentley T.
Published: April 2005

The radiant flux in the Hg resonance lines just inside the wall of a lamp with an inside diameter of 35–36 mm is given for currents 0.4−2.0 amp and various bulb temperatures and rare gas fillings. The intensity of the 1850 line ranges from 12 to 34% of that of the 2537 one, with the highest ratios occurring when both arc current and bulb temperature are at the upper end of the ranges used. Since this result is contrary to what one would expect with single-stage excitation of the 1850 line, one must assume that this line is excited mainly by 63P–61P1 transitions when arc current and mercury vapor pressure are both relatively high. A rough estimate of the frequency of 63P2–61P1 transitions, compared to those from the ground level to 61P1 confirms this conclusion.
Ultrasonic Viscoelastic Properties of Associated Liquids
Authors: Meister R. , Marhoeffer C. J. , Sciamanda R. , Cotter L. , Litovitz T.
Published: April 2005

Measurements of ultrasonic propagation of longitudinal and shear waves over a wide frequency and temperature range were made in an homologous series of associated liquids, butanediol 1,3, 2-methyl pentanediol 2,4 and hexanetriol 1,2,6. In each case, the absorption data demonstrated the presence of shear and structural or volume viscosities which are of the same order of magnitude and have the same temperature dependence. In order to account for the shear and compressional data, it was necessary to assume that a distribution of relaxation times excited. It was found that a different distribution was necessary for the compressional data than that used in accounting for the shear relaxation data. Comparison of the average relaxation time of structural and shear processes in the associated liquids shows that they are very close in value departing by a maximum of a factor of 4. In addition, it was found that the shear modulus was about 20 to 30% of the high-frequency compressional modulus. The ratio of shear compressional modulus in these liquids was very close to the values found in typical solids, even though the magnitudes of the moduli of the liquids was about a factor of 10 smaller than found in typical solids. The temperature dependence of the shear modulus and the relaxation part of the compressional modulus was found to be the same. The moduli linearly increase with decreasing temperature in a manner which is not accounted for by the Eyring-Hirai theory. It was found that the Tobolsky-Leaderman Ferry reduction formula, which is based on the assumption that the moduli are proportional to temperature, does not hold for these liquids and probably not for any high frequency visco-elastic data not associated with an ``entropy'' modulus. The data in the associated liquids were reduced by using the proper temperature dependence of the moduli. In considering the data of high frequencies, the absorption could not be accounted for by the same distribution which was used to fit the velocity data. At frequencies well above the dispersion region it was found that an attenuation set was independent of frequency. This appears to be characteristic of these liquids at very high frequencies and viscosities. At this time, there seems to be no acceptable mechanism to explain this type of loss. The latter authors have suggested that the hysteresis effect is not related to the viscous flow mechanism causing absorption at the lower frequencies and viscosities.
Theory of a Negative-Resistance Transmission Line Amplifier with Distributed Noise Generators
Authors: Chang K. K. N.
Published: April 2005

A transmission line with distributed positive and negative resistances as well as with distributed noise generators is treated. Gain and noise factor are derived as a function of boundary conditions, matching conditions and distributed noise. It is found that low-noise amplification can be achieved on such a line provided the line is characterized by high gain per unit length, high total gain, good matching, and low distributed noise. A distortionless active line for such low-noise amplifiers appears attractive.
Thermal Emission of Alkali Ion Pulses from Clean and Oxygenated Tungsten
Authors: Minturn Robert E. , Datz Sheldon , Taylor Ellison H.
Published: April 2005

The spontaneous emission of positive ions from a heated tungsten filament occurs as pulses, a single pulse releasing as many as 106 ions in less than 100 μsec. The pulses are composed mainly of potassium ions, present as impurities in the tungsten lattice. It is suggested that the emission of positive ions in the form of bursts is dependent upon the existence of edge dislocations in the metal. At temperatures where the formation of an adsorbed layer is possible, oxygen has a very pronounced effect upon the rate of emission of positive ion pulses.
Acoustic Resonance in Solid Propellant Rockets
Authors: McClure F. T. , Hart R. W. , Bird J. F.
Published: April 2005

Attention is drawn to the fact that the solid propellant must, in general, be considered as one of the acoustic media in a rocket motor. The viscoelastic properties of the solid along with those of the burned gases determine the characteristic modes of the system corresponding to the particular boundary conditions imposed on these media by the metal components. In addition, these properties of the media contribute strongly to the selection of the regions of stability and instability of the system and therefore to the intermittent and sporadic nature characteristic of resonant burning in solid propellant motors. Calculations are carried out to illustrate the general nature of the phenomenon, and the relationship of these studies to a variety of experimental observations is discussed.
Detection of Metastable Atoms and Ions
Authors: Hagstrum Homer D.
Published: April 2005

Experimental work is presented concerning the detection of metastable singly charged ions by means of electron ejection from contaminated metal surfaces. By the use of suitable retarding potentials one can cause the current of reflected ions to cancel very nearly the current of electrons ejected by the ground state ions. This method increases the ratio of metastable signal to background signal by a factor of 300 or more and is comparable to what can be done by modulation of the metastable component. Some comments concerning the detection of metastable atoms by means of Auger electron ejection processes are included.
Stacking Faults in Zinc
Authors: Fourdeux A. , Berghezan A. , Webb W. W.
Published: April 2005

Configurations of individual dislocations in zinc have been studied by electron transmission microscopy and by x-ray diffraction microscopy. Loops of sessile dislocation have been observed surrounding stacking faults lying on (0001) planes. These loops were evidently formed by condensation of point defects. Changes in loop size with climb of the surrounding dislocation have been observed occurring in the electron microscope. Separation of glissile dislocations into partial dislocations separated by stacking faults on (0001) planes have also been observed. Various interactions among the several types of dislocations occur.
Evolution of Gases and Ions from Different Anodes Under Electron Bombardment
Authors: Young J. R.
Published: April 2005

With the aid of a bakeable mass spectrometer a study has been made of the material evolved from Ag, Cu, Ni, Mo, Ta, Ti, and W anodes exposed to oxide cathodes. Chlorine was found to be evolved from all the anodes during the first period of bombardment. No evidence of the dissociation of the thin films of BaO or SrO on the anodes was obtained, suggesting it does not play a significant role in oxide cathode poisoning. It is believed that the Cl evolution may be responsible for the early slump in emission commonly observed at low anode voltages from oxide cathodes. Evolution of O+ ions was observed from oxidized Cu, Ni, Mo, Ta, and Ti with efficiencies up to approximately 10−5 ions/electron for electron energies of 90 ev and current densities of 10 ma/cm2. This O+ evolution reduced considerably the dc emission capabilities of the oxide cathodes. It was found that heating the anodes from 700° to 1000°C for long periods of time does not always eliminate all evolution products caused by electron bombardment. Hydrogen was observed to be evolved from Ti and O+ ions were observed from formerly oxidized Cu, Ni, Mo, and Ta immediately after outgassing at temperatures less than 1000°C.
Energy Distribution and Cooling Effect of Electrons Emitted from an Arc Cathode
Authors: Lee T. H.
Published: April 2005

The energy distribution and the average cooling effect of electrons emitted by the T-F process are calculated over a wide range of temperatures and electric fields for several values of work functions. It is shown that at low temperatures, the average cooling effect approaches zero and at high temperatures, it is approximately equal to the reduced work function. The limitation of the validity of reduced work function can be easily seen.
Effect of Atomic Interaction Potential on Defect Production in Metals
Authors: Brown E. , Goedecke G. H.
Published: April 2005

The cascade of displaced atoms in metals, induced by high energy radiation, has been investigated, with the assumption of a screened coulomb interaction between atoms. The problem was treated stochastically on an IBM 650 electronic computer for several different models. The comparison of our results with those for which a hard sphere interaction has been used shows only a slight decrease in the expected number of atomic displacements.
On the Neutron Bombardment Reduction of Transistor Current Gain
Authors: Easley J. W. , Dooley J. A.
Published: April 2005

Detailed measurements of the fast-neutron and gamma-ray bombardment behavior of germanium-alloy-transistor current-gain have been obtained concurrent with exposure. These data indicate that previously reported analyses, which lead to a linear dependence of common-base current-gain on fast neutron exposure, yield a good approximation for the npn device, but are not of general validity for the pnp germanium transistor. The extent of departure from the linear approximation depends on the width and conductivity of the base-region and can be appreciable in many cases of practical interest.

For the pnp germanium transistor it is necessary to take additional account of both changes during bombardment of the minority-carrier recombination rate at bombardment introduced and initially present recombination centers and changes in the width of the collector junction depletion layer. Observed bombardment curves are in good agreement with an analysis which includes these effects. From initial slopes of the current-gain bombardment curves, values of the product of fast-neutron-exposure times minority-carrier-lifetime at bombardment introduced recombination centers are 9.7×107 for 2.7 ohm-cm p-type and 14.2×107, 6.0×107, and 1.3×107, for 3.6 ohm-cm, 1.2 ohm-cm, and 0.2 ohm-cm n-type germanium, respectively, in units of sec-neutrons/cm2.
Bias in Ferroelectric Colemanite
Authors: Fatuzzo Ennio
Published: April 2005

The question of the existence of an intrinsic bias in colemanite above the Curie point is studied and compared with experimental results. It is concluded that a bias does exist above the Curie point and that it is completely responsible for the pyroeffect experimentally observed there. Some formulas are derived, connecting the pyroeffect and the intrinsic bias, and are compared with data available in the literature.
Surface Wave Excitation and Propagation
Authors: Keller Joseph B. , Karal Frank C.
Published: April 2005

A geometrical theory is developed for the analysis of surface wave excitation and propagation. The surfaces along which the surface waves propagate may be either curved or flat, and may have either constant or variable properties. The theory is based on the concept of a complex or imaginary ray. The excitation coefficient which enters the theory is determined from the solution of a canonical problem—that of a line source over an impedance plane. Then the theory is applied to the surface wave excited by a line source, on a wedge with variable surface impedance. The result agrees precisely with the asymptotic form of the exact solution. Another application is made to the surface wave excited on a cylinder by a line source. The result also agrees with the exact solution.
Range of Radiation Induced Primary Knock-Ons in the Hard Core Approximation
Authors: Holmes D. K. , Leibfried G.
Published: April 2005

The slowing down of a primary displaced atom of high energy in a solid is investigated in detail. Physically interesting quantities, such as the total distance travelled and the vector distance to the end of the path, are discussed in terms of certain averages for hard core potentials with general dependence of the core radius on energy. These averages are explicitly calculated for a screened Coulomb potential for the purpose of comparison with experimental ranges observed in different metals. Theoretical values for the range can be derived. Comparison with the experimental data gives a value for the screening radius of the interaction potential which is about twice the value originally suggested by N. Bohr.
Displacement of the Sulfur Atom in CdS by Electron Bombardment
Authors: Kulp B. A. , Kelley R. H.
Published: April 2005

The threshold for displacement of the sulfur atom from a lattice point in CdS has been measured to be 8.7 ev. This is accomplished with 115-kev electrons. This is also the threshold for the production of green edge emission centers and of centers for a red fluorescence band with a maximum intensity at about 7200 A. In crystals which show edge emission before bombardment, the edge emission is removed by electron bombardment in the energy range 2.5 to 200 kev. The red luminescence is not removed by electron bombardment but increases in intensity with bombardment above the threshold. The radiation ``annealing'' of the edge emission is accomplished even in crystals which do not thermally anneal. A model is proposed with the sulfur interstitial atom the center for edge emission, and the sulfur vacancy the center for the red emission band.
Photoeffects in Nonuniformly Irradiatedp-nJunctions
Authors: Lucovsky Gerald
Published: April 2005

A theoretical basis is provided for the interpretation of photoeffects observed in nonuniformly irradiated p-n junctions. Differential equations describing the junction photovoltage are developed through an application of the continuity and diffusion equations. Solutions of the small-signal steady-state photoeffect equation indicate that the effects of nonuniform irradiation become increasingly important as the ratio of the lateral to the transverse resistance increases. α, a parameter introduced in this paper and designated as the lateral-fall off parameter, is a measure of this resistance ratio. The lateral photovoltage resulting from nonuniform irradiation can be eliminated by reverse biasing the junction into saturation. Experimental curves in agreement with the predictions of the analysis are presented.
Simple Radiant Heating Method for Determining the Thermal Diffusivity of Cellulosic Materials
Authors: Martin Stanley B.
Published: April 2005

A simple radiometric method for the determination of the thermal diffusivity of poorly conducting sheet-form materials such as cellulosic kindling fuels is described. The method is a dynamic one based on the ``long time'' solution of the heat-conduction equation for the infinite slab with constant heat-input rate, and utilizes fine-wire thermocouples laminated between sheets of the material (whose diffusivity is required) to measure rates of temperature rise at various depths. The geometry of the system is designed to satisfy as many as possible of the boundary conditions imposed on the mathematical model. The magnitude of errors introduced by violating the other boundary conditions is discussed in connection with the results of measurements on α-cellulose.

The value of the thermal diffusivity of α-cellulose containing two percent carbon black and whose density is 0.68 g/cm3 was found to be 1.06±0.06×10−3 cm2/sec.
Ferromagnetic Resonance in Polycrystalline Ferrites Using Circularly Polarized Radiation
Authors: Zeender R. J. , Schlömann E.
Published: April 2005

If the saturation magnetization is much smaller than the anisotropy field, the resonance curves observed in polycrystalline ferrites have a well-defined structure with several peaks or shoulders. (See works cited in footnotes 1 and 2.) The use of circularly polarized radiation facilitates a clear identification of the peaks. In cubic materials the central peak (arising from grains which have a [110] direction aligned with the dc field) is partially excited by both senses of circular polarization, whereas the two outer peaks or shoulders are excited only by the positive sense of circular polarization. Experimental results obtained in the compensation region of the nickel ferrite-aluminate system agree well with the theoretical predictions. These results rule out the possibility that the additional absorption peaks are due to an exchange resonance.
Intervalley Noise
Authors: Price P. J.
Published: April 2005

A theory is developed for the spectrum of electrical noise due to electron transitions between several quasi-isolated groups of states, in the general case where each group may carry part of an electric current. It is applied to the noise due to transitions between valleys of the conduction band of germanium, and the possibility of observing this noise is discussed using the data of Weinreich, Sanders, and White on the frequency of intervalley transitions.
Transport of Noise at Microwave Frequencies through a Space-Charge-Limited Diode
Authors: Vivian W. E.
Published: April 2005

Several analyses of the transport of cathode shot noise through a space-charge-limited diode at microwave frequencies have been published to date. Each of these analyses has been beset by inconsistencies arising from assumptions of monovelocity perturbation flow, direct or reflected. A new method of analysis of diode flow eliminating this problem has been developed. Numerical results based on this method are presented here. Attention is restricted to the now classical problem of one-dimensional longitudinal confined flow.

The magnitude and variation with distance of the so-called beam noise invariants is shown for a range of diode operating conditions. These calculated results, based for economy on an approximate static flow model, essentially substantiate the qualitative expectations suggested by prior analyses, and fit what little experimental data are available.

The method of analysis employed in the calculation of the numerical results comprises a linear multistream formulation, based on representation or approximation of the perturbation particle density for the noise flow as a composite of singular impulse streams, N in number, along characteristic trajectories in the velocity-distance phase space. The set of N coupled first-order linear differential equations resulting is solved by simultaneous numerical extrapolation.
On the Flow of a Non-Newtonian Liquid on a Rotating Disk
Authors: Acrivos A. , Shah M. J. , Petersen E. E.
Published: April 2005

The equations describing the flow of a power-law non-Newtonian fluid on a rotating disk have been solved in general form. This makes it possible to calculate how the shape of an initial surface contour will vary with time and to investigate the possibility of producing uniform films by applying the materials to a rapidly spinning disk. It is shown that the latter process, which has potential industrial applications, has a much better chance of succeeding if the fluid is Newtonian than if it is not, in the sense that whereas for a Newtonian substance centrifugation will smooth out irregularities in the surface contour, for a non-Newtonian fluid even an initially uniform film thickness will be deformed by rotating the plate.
Photoemission in the Photovoltaic Effect in Cadmium Sulfide Crystals
Authors: Williams Richard , Bube Richard H.
Published: April 2005

A study has been made of the photovoltaic effect in Cu–CdS cells and related systems, associated with undiffused metal-semiconductor junctions. The photovoltaic current has been shown to result from the photoemission of electrons from the copper metal into the CdS crystal. Direct evidence is presented for this conclusion, and the conditions required for the photoemission process to occur are demonstrated by several experiments. Important factors contributing to the efficiency of Cu–CdS photovoltaic cells of this type are: (a) the optical properties of copper, (b) the rectifying contact between the metal and CdS, (c) the good conductivity and high optical transparency which can be achieved in CdS crystals, and (d) the favorable relation between the work function of copper and the electron affinity of CdS.
Diagrams Representing States of Operation of a General Thermocouple
Authors: Boerdijk A. H.
Published: April 2005

The state of operation of a thermocouple of which (a) the bars have an arbitrary shape; (b) the properties of the materials are arbitrary functions of temperature; and (c) the composition is, under certain restrictions, inhomogeneous and anisotropic depends on three independent parameters: the current I and the temperatures T1, T2 of the junctions. If T2 is kept constant, operating characteristics, such as curves of constant output power or efficiency, can be plotted in an I, (T2−T1) diagram. The existence of regions of generation of electricity and of cooling is proved. These regions are investigated. Possible generalization and reduction of the diagram are discussed. As an illustrative example, the cooling region of a general couple with temperature independent properties is dealt with.
Time Discrimination in Solid-State Infrared Quantum Counters
Authors: Jelley J. V.
Published: April 2005

The paper discusses various considerations in the practical realization of the infrared solid-state quantum counter recently proposed by Bloembergen. It is suggested that a high degree of discrimination between the quantum to be counted, and the optical pumping flux, could be attained by a time-sequence switching system; it is estimated that an isolation of ∼160 db might be required. The proposal demands that at least one of the levels in the crystal have a long lifetime, and a simple expression is derived for the overall efficiency of the detector in this case. An additional gain in efficiency and isolation would result if ``double pumping'' were used, with detection in the ultraviolet. In conclusion a suggested layout of components is presented incorporating the switching scheme discussed herein.
Power Flow and Stored Energy in Thin Electron Beams
Authors: Rigrod W. W.
Published: April 2005

The kinetic and electromagnetic components of ac power and stored energy are evaluated for space-charge waves along thin drifting beams of simple geometry. It is found that: (a) when a modulated beam is decelerated, it radiates power into the surrounding space; (b) when both fast and slow waves are excited by a common source, the real kinetic power varies periodically with distance, exchanging energy with the electromagnetic field; and (c) when a finite-area beam is current modulated with zero ac velocity, the total power need not be zero.

The energy transport velocity of a space-charge wave is shown to equal its group velocity, when the time-average stored energy is properly evaluated. A small portion of the stored kinetic energy propagates, together with the field energy, as an electromechanical wave along the beam. The larger part of the kinetic energy, which can be positive or negative, is transported by the motion of the beam itself.
Uniform Silicon p-n Junctions. I. Broad Area Breakdown
Authors: Batdorf R. L. , Chynoweth A. G. , Dacey G. C. , Foy P. W.
Published: April 2005

Small area silicon p-n junctions have been made which are free from exposed edges and dislocations passing through the space-charge region. It is believed that the space-charge regions of these junctions more closely resemble plane parallel geometries than any studied similarly hitherto. The avalanche breakdown phenomena in these uniform junctions are shown to be drastically different from those occuring in junctions that contain many dislocations. A comparison is made between the uniform junctions and one that is similar except that it possesses two breakdown-inducing sites, probably dislocations. In the latter junction the reverse characteristic shows two slightly separated rapid increases in current which coincide, biaswise, with the formation of two isolated light-emitting microplasmas, the occurrence of characteristic microplasma noise, and two singularities in the charge-multiplication characteristics. The uniform junctions show no such phenomena at intermediate voltages, breakdown occurring at a voltage roughly twice that at which the microplasmas form and which was previously thought typical for the given material resistivity. The light emission pattern accompanying breakdown in the uniform junctions appears more diffuse (giving rise to the term—macroplasma) than in nonuniform junctions where it normally appears as an array of intense local spots (microplasmas). It is concluded that microplasmas are not a necessary accompaniment of avalanche breakdown in silicon, but that they tend to occur where there are field or lattice inhomogeneities.
Uniform Silicon p-n Junctions. II. Ionization Rates for Electrons
Authors: Chynoweth A. G.
Published: April 2005

Charge multiplication as a function of reverse bias has been studied in a number of uniform silicon p-n junctions (junctions free from defects which promote local avalanche breakdown sites). From the multiplication characteristics new data have been derived for the field dependence of the ionization rate (α) for electrons. As previously found in junctions containing dislocations, α obeys the empirical relation α=α∞ exp (−b/E), where α∞ and b are constants and E is the field. Thus, this law is not simply a consequence of distortions to the junction introduced by dislocations or other microplasma-inducing defects.

The ionization rates and breakdown voltages for the uniform junctions can be made consistent with older data (for nonuniform junctions) if the junction fields, as determined from capacitance measurements, in the new junctions are multiplied by 0.65. The most obvious interpretation of this experimental fact is that breakdown is made relatively easier at defects because the field is actually higher by a factor of 1.55. Possible causes of such an enhancement are discussed together with alternative hypotheses for the different ionization rates.
On the Kinetics and Mechanism of the Precipitation of Lithium from Germanium
Authors: Carter J. R. , Swalin R. A.
Published: April 2005

The kinetics of precipitation of lithium from germanium have been investigated and the following variables have been studied: (a) crystal source; (b) preannealing treatments prior to the introduction of lithium; (c) the effect of selective impurity additions, namely, oxygen and copper. The precipitation process can be described as following the law given below: logC/C0=exp[−(t/τ)n].

Upon saturation at elevated temperatures, (about 425°C), n is found to be 32 for the first part of the process and 1 for the later part of the process. Upon saturation at low temperatures, however, n is found to be ½. It is suggested that this results from the nonuniform distribution of lithium in the crystal prior to precipitation.

Nucleus number densities varying by orders of magnitude were obtained from different crystals. It was found that a preannealing treatment at 900°C was sufficient to increase the nuclei number densities for all crystals and the differences tend to disappear upon the preannealing treatment.

Doping with oxygen tended to increase very markedly the number density of nuclei whereas doping with small amounts of copper (several orders of magnitude less than lithium present) decreased the number density of nuclei by about an order of magnitude. Interpretation of these results suggests that an impurity, consisting either of particles or oxygen-vacancy pairs, is catalyzing the precipitation process.
Beam Refrigeration by Means of Large Magnetic Fields
Authors: Adler Robert , Wade Glen
Published: April 2005

The resistive loading which an electron beam produces in an adjacent structure can be made to exhibit a very low noise temperature. This is achieved by coupling to the fast cyclotron wave in a large magnetic field; the noise temperature at a given signal frequency is shown to be equal to the cathode temperature times the ratio of signal frequency to cyclotron frequency.

An experiment is described in which this ratio is 19. The coupling structure interacts with the fast cyclotron wave but rejects the slow cyclotron wave. A noise temperature of 186°K is measured.

In conclusion, it is shown that the large magnetic field required for beam cooling need not extend throughout the tube.
Low-Temperature Transport Properties of Commercial Metals and Alloys. IV. Reactor Grade Be, Mo, and W
Authors: Powell Robert L. , Harden James L. , Gibson Edward F.
Published: April 2005

The thermal conductivity, electrical resistivity, Lorenz ratio, and thermoelectric power are given in the temperature range 4°–120°K for four reactor grade metals: beryllium with sample axis parallel to the pressing axis, beryllium with sample axis perpendicular to the pressing axis, molybdenum, and tungsten, the latter two doped with ThO2. Within the given temperature range the molybdenum and tungsten show slight maxima in thermal conductivity, the beryllium does not. The various components of the electronic and lattice thermal conductivities and resistivities are resolved. The residual electrical resistivities are, respectively, 0.64, 1.01, 0.57, and 0.16×10−6 ohm-cm.

The Lorenz ratios for molybdenum and tungsten show both maxima and minima and are always below the Sommerfeld value. The ratios for the beryllium samples have broad maxima and generally are above the Sommerfeld value. The thermoelectric powers of the samples with respect to pure copper are negative for the higher temperatures and positive for the lower temperatures.
Magnetization of a Dilute Suspension of a Multidomain Ferromagnetic
Authors: Bean C. P. , Jacobs I. S.
Published: April 2005

The observed magnetization curve of a dilute suspension of carbonyl iron powder, type E, is shown to be closely that one would derive from consideration of a dilute assembly of randomly oriented, single-crystal, multidomain spheres. The deviations are in the directions expected from the effects of stress and non-spherical clumping. The effects of packing and the applicability of various laws of approach to saturation are discussed.
Thermionic Properties of UC
Authors: Haas George A. , Jensen John T.
Published: April 2005

Thermionic emission measurements using pulse techniques have been obtained from UC-coated W filaments in the temperature range of 1200°–2100°K. From the slope and intercept of the Richardson plot, a value of φ=2.94 ev and A=33 amp/cm2 deg2 was indicated. There is evidence that the energy required for electrons to escape at low fields might be several tenths ev higher than the 2.94 ev value.
Criteria for the Choice of a Superconducting Bolometer
Authors: Lalevic Bogoljub
Published: April 2005

The usefulness of the superconducting bolometer was recognized a long time ago. All experimental data obtained up to now are far below the calculated value for a sensitivity of such a bolometer, because of the presence of the noise in the transition region of a superconductor. We have presented the correlation between the noise and the value of the surface boundary energy (interface between normal and superconducting laminas) and given on this basis the criteria for the choice of a superconducting bolometer. Attempt has been made to evaluate the noise on the basis of the Thomas-Fermi approximation.
Electrostatic Acceleration of Microparticles to Hypervelocities
Authors: Shelton H. , Hendricks C. D. , Wuerker R. F.
Published: April 2005

By electrostatic methods, μ-diam spheres of iron have been accelerated to hypervelocities. Techniques have been developed to give single impacts in vacuum of measured incident velocity, mass, and position.
Resistance to Potential Flow through a Cubical Array of Spheres
Authors: Meredith Robert E. , Tobias Charles W.
Published: April 2005

Precise conductivity measurements on models sectioned out from a cubic lattice of spheres in a continuous medium indicate that the effective conductance of such a system deviates from the values predicted by Lord Rayleigh's analytic solution of this potential distribution problem. Deviations become particularly significant when the spheres approach close packing, and when the conductance of spheres is much greater than that of the continuum. By use of a different function for potential, and by consideration of higher terms in the series expression for the potential in the continuous phase, Rayleigh's results are modified, yielding an analytical expression that represents effective conductance satisfactorily in the concentration region approaching close packing.
Electron Microscopic Study of Thin Films of the Aluminum-Copper Eutectic Prepared by a Melting Method
Authors: Takahashi Noboru
Published: April 2005

Thin films of the Al-Cu eutectic (67 wt% Al, 33 wt% Cu) were prepared by the melting method previously described and examined by electron microscopy. The lamellar structure of this eutectic was revealed so clearly that the contrast of the image obtained was comparable to that obtained by a replica method, which proved that the present film represented the same structure as the massive specimen. Electron diffraction study revealed which lamella belongs to the κ or θ phase and permitted the determining of the relative crystal orientation between two types of lamellas.