bluuebunny/crossref_metadata_2025 huggingface dataset:
High Field Electron Emission from Irregular Cathode Surfaces
Authors: Lewis T. J.
Published: April 2005

Electron emission from a cathode surface produced by an applied field E is enhanced by the presence of projections on the emitter surface which cause a local increase in E. The nature of this enhancement factor μ(z), which is a function of the distance z from the cathode, is discussed more fully than hitherto and its magnitude is calculated for certain ideal but realistic geometries. Although such a factor may be large on the surface (z=0), it decreases rapidly as z increases so that the mean field magnification μ̄(z), which is required in the Schottky thermionic emission theory, is unlikely to be >2 and is probably near to unity even for fields as great as 5×105 v/cm. This fact will mean that the Fowler-Nordheim theory frequently used to explain emission results at these fields is not applicable and that a Schottky theory should be used.

It is also shown that μ̄(z) is itself field dependent and produces departures from the Schottky law in such a way that the slope of the current vs E½ plot increases rapidly for E<103 v/cm, remains approximately constant for 103<E<104 v/cm, and then increases again at higher fields. A similar reasoning shows that deviations from the Fowler-Nordheim law for fields >106 v/cm can also be expected.

Finally, the assumption of a constant emitting area for rough cathodes is also shown to give departures from the emission laws in such a manner that the estimated current density at high fields is appreciably less than the expected values.

These deductions help to explain some of the anomalous results frequently found in many conduction experiments in gases and liquids.
Hexagonal Microstructure of Ice Crystals Grown from the Melt
Authors: Truby Frank K.
Published: April 2005

Electron microscopy of etched and nascent surfaces of single ice crystals shows a characteristic microstructure of elongated, hexagonal prisms. The small hexagonal units vary greatly in size with an expected width of the order of 3 microns and a length of 6 microns. The coordination among microcrystalline units characterizes a particular single crystal, the size of which may be determined by processes of freezing and subsequent history, but the sizes of the microcrystalline units of which they are composed appear to be independent of the rates of freezing. The etched surfaces show that the center of the hexagonal unit etches to a greater depth than does the outer area, indicating a higher degree of crystal disorder along the axis of symmetry.

Ice surfaces in process of growing from the melt also appear to consist of hexagonal pyramidal pits which are built up by concentric steps around the C-axis. This structure appears to be consistent with that of the etched surfaces. Observations of growing-ice surfaces formed from cesium fluoride solutions reveal that the fluoride impurity tends to reduce the prominence of the pyramidal microstructure in a manner dependent upon concentrations such that the structure disappears for concentrations greater than 10−3 M.
Dynamic Determination of the Compressibility of Metals
Authors: Goranson Roy W. , Bancroft Dennison , Burton Blendin L. , Blechar Theodore , Houston Edwin E. , Gittings Elisabeth F. , Landeen Stanley A.
Published: April 2005

Equation of state data for Duralumin in the pressure range from 0.1 to 0.3 megabar have been determined dynamically by measuring shock and free surface velocity electrically in a plate of 24 ST Duralumin that has been stressed by a high explosive detonation. A theory is presented which allows comparison with data obtained by other experimenters, and which yields the relationship between pressure and compression either at constant entropy or constant temperature. The empirical form chosen for the equation of state (p=αμ+βμ2) expresses the pressure as a quadratic function of the compression. Experimental techniques are described in detail. Five points are given for the equation of state of Duralumin in the pressure range from approximately 0.15 megabar to 0.33 megabars. Some data are also presented for cadmium and steel.
Total Emissivities and Absorptivities of Some Commercial Surfaces at Room and Liquid-Nitrogen Temperatures
Authors: Zimmermann F. J.
Published: April 2005

The heat transferred by radiation was measured between surfaces at room temperature and liquid-nitrogen temperature. The surfaces used were various combinations of electroplated gold and silver and polished copper sheet. From the test data, the approximate total emissivities of the room-temperature surfaces and the total absorptivities of the liquid-nitrogen surfaces were computed.

The results of these tests indicated that electroplated silver surfaces have lower emissivities and absorptivities than equivalently treated electroplated gold surfaces in this temperature range. The best surface tested was a special, bright, unbuffed silver-plated surface. This surface is known to the trade as ``silver lume.'' The room-temperature emissivity of this surface was approximately 0.017, and the absorptivity at 77.3°K for radiation from a 300°K surface was about 0.0083. These are the lowest values at these temperatures of which we have knowledge.

It was found that the electroplated surfaces were best used without buffing or any mechanical working of the surface. It is believed that cold working of the metal surface increases its emissivity and absorptivity by increasing its electrical resistivity.
Gettering of Gas by Titanium
Authors: Stout Virgil L. , Gibbons Martin D.
Published: April 2005

Titanium metal has been studied as a getter for oxygen, nitrogen, carbon dioxide, air, water vapor, hydrogen, and methane. Titanium above 700°C will getter oxygen, nitrogen, and carbon dioxide. Hydrogen is absorbed by titanium in the temperature range of 25 to 400°C. Water vapor and methane are readily sorbed when the metal is operated at both elevated and reduced temperatures. Large quantities of gases can be sorbed; sorption of ten to ninety atomic percent is possible. When saturated with gas, the metal becomes brittle and is easily fractured. Hydrogen gas is the only gas which can be released by heating after it has been sorbed by titanium.
Stress-Strain Relations in Snow under Uniaxial Compression
Authors: Landauer Joseph K.
Published: April 2005

Two types of tests were performed on the uniaxial compression of snow; experiments at constant strain rate and at constant load. The strain rate can be represented as the product of functions of density, stress, temperature, and time. For densities between γ≃0.3 g/cc and γ≃0.6 g/cc the strain rate is proportional to (γice−γ)/γ to the fourth power. The strain rate varies linearly with stress for low stresses (2<σ<100 g/cm2) but increases to an approximately cubic relationship at higher stresses (1<σ<5 kg/cm2). An activation energy of about 14 000 cal/mole can be derived from the temperature dependence. In the constant load tests the strain is proportional to the time to a power of about 0.8. The effect of snow type is small, being less than the relatively large experimental scatter encountered.
Angular Distribution of Multiply Scattered Gamma Radiation from a Plane Isotropic Source
Authors: Berger Martin J.
Published: April 2005

A method is given for calculating, within the framework of the moment-method of Spencer and Fano, the angular distribution of radiation from a plane isotropic source. Essential use is made of the simplification introduced by a geometrical feature of radiation from such a source. Sample calculations are presented for a 1-Mev source in water.
Measurement of Microwave Diffraction from a Long Slit in a Thin Conducting Plane
Authors: Hirshfield Jay L. , Zieman Clayton M.
Published: April 2005

This paper gives the results of measurements of the fields diffracted from a long narrow slit in a large conducting plane, when a uniform plane is incident. The results for two polarizations are shown.
Backscattering from Wide-Angle and Narrow-Angle Cones
Authors: Felsen Leopold B.
Published: April 2005

Solutions are obtained for the diffraction of the waves radiated by scalar and vector point sources on the axis of a semi-infinite cone. The scalar problems are solved by the method of characteristic Green's functions to yield directly various alternative representations whose different convergence properties are discussed; the vector problem is solved by an application of spherical transmission line theory. To evaluate the plane wave scattering observed far from the cone tip, a highly convergent contour integral representation is selected and evaluated approximately for the special case of backscattering from cones having large and small apex angles. The results for the large-angle cone exhibit the transition from a backscattered spherical wave to a plane wave as the cone degenerates into an infinite plane.
Diffraction by Apertures
Authors: Huang Chaang , Kodis Ralph D. , Levine Harold
Published: April 2005

The diffraction of plane electromagnetic waves by apertures in a plane screen which is infinitesimally thin and perfectly conducting is studied both theoretically and experimentally. The theoretical analysis employs a dyadic Green's function to develop vector formulas for the scattered fields, and from these formulas integral equations are obtained for the aperture distributions. The vector representation makes possible a compact demonstration of the electromagnetic form of Babinet's principle by means of which one may extend the aperture analysis to complementary disks. The integral equations are then used to construct a variational principle for the aperture transmission coefficient.

Detailed analysis and numerical computations are carried out for two configurations. For the circular aperture a first-order vector trial function with frequency dependent coefficients is chosen for the aperture distribution. The approximate transmission coefficient is found to agree closely with the exact value in the region 2πa/λ≤3. For elliptical apertures a zeroth-order approximation is evaluated using a one-component trial function. Numerical results are given for minor-to-major axis ratios of ½ and ⅓.

Transmission coefficient measurements were carried out in the 24 000 megacycle band (λ=1.25 cm) using an image plane technique. The apparatus was first calibrated with the exact solution of the circular aperture. The approximate results calculated for elliptical apertures are then seen to be in good agreement with the measurements over the accessible range.
Measurement of Carrier Lifetimes in Germanium and Silicon
Authors: Stevenson Donald T. , Keyes Robert J.
Published: April 2005

The decay of photoconductivity has been used to measure the lifetime of excess carriers in rectangular samples of germanium and silicon. The sample is illuminated by a short pulse of light and the sample lifetime obtained from an oscilloscope display of the decay of photoconductivity. Analysis of the solution of the diffusion equation yields methods of measuring the bulk lifetime, the surface recombination velocity, and the diffusion constant.
Internal Friction of Metal Single Crystals
Authors: Weertman Johannes
Published: April 2005

Semiquantitative calculations were made of that portion of the internal friction of annealed and moderately cold-worked metal single crystals which is due to dislocation motion. The calculations were made on the basis of a qualitative theory of Nowick. It is shown that Nowick's theory leads to reasonable orders of magnitude of the observed internal friction and changes of the modulus of elasticity. At low temperature or at high frequencies (megacycle range) Nowick's hysteresis mechanism becomes inoperative and theories of Koehler and of Eshelby have to be considered to calculate the internal friction.
On Power Spectra and the Minimum Detectable Signal in Measurement Systems
Authors: Freeman J. J.
Published: April 2005

A least upper bound for the minimum detectable signal of a receiving system whose input is a periodic wave form plus interference is specified in terms of the first and second moments of the rectified output. Also, it is shown that the power spectrum of the rectified output (together with the impedance characteristic of the output meter) serves to establish the first and second moments of the meter deflection for either of the following two cases:

(1) The rectified output operates a meter, and the difference in meter readings with the signal on and off constitutes the observation from which the message is inferred.

(2) The rectified output feeds a synchronous detector whose meter reading is directly proportional to the message. Here we require that there be no input noise which is modulated at the synchronous frequency.
Patch Effect for the Thermionic Emission from Polycrystalline Tantalum
Authors: LaBerge W. B. , Munick R. J. , Dezoteux J. A. , Whalen J. F. , Coomes E. A.
Published: April 2005

The slope modifications for the Schottky line implied by simple patch theory have been obtained at high fields for thermally etched tantalum filaments. For ac-aged filaments, only the usual low field patch modification was obtained. For dc-aged filaments an additional anomaly at higher fields was obtained, simultaneous with the appearance of the dc etch pattern on certain faces of the crystal grains. This high field anomaly, consisted of a double break in slope, and appeared at an average patch field about 50 times the patch field due to the distribution of crystal faces.
Inertial Impaction of Aerosol Particles on Cylinders
Authors: Wong J. B. , Ranz W. E. , Johnstone H. F.
Published: April 2005

The inertial impaction of aerosol particles on cylinders was investigated to determine the relationship between the efficiency of impaction and the inertial parameter, the Reynolds number of flow, and the effect of interception. The impaction of sulfuric acid aerosols of nearly uniform size ranging from 0.6 to 1.4 microns diameter, on two platinum wires, 29 and 83 microns diameter, and two tungsten wires, 53 and 106 microns diameter, was measured at several velocities of flow past the wires. Reynolds numbers ranged from 13 to 330. For values of the square root of the inertial parameter Ψ½ below 1.4, the experimental efficiencies of impaction agree with those predicted by Langmuir and Blodgett for potential flow and by Landahl and Herrmann for a Reynolds number of 10. The experimental values are higher than the calculated values for Ψ½ greater than 1.4. The theoretical prediction that a critical value of Ψ½ exists at approximately ¼, below which inertial impaction does not occur, was verified.
Resonance Absorption of Neutrons by Spheres
Authors: Wigner E. P. , Creutz E. , Jupnik H. , Snyder T.
Published: April 2005

By concentrating uranium into lumps, one can decrease its resonance absorption as compared with the resonance absorption of the same amount of uranium spread out uniformly in a moderator. It is shown here that this decrease is caused principally, not by the diminished over-all density of the neutrons at the lump, but by their changed energy distribution. This shows deep minima at the resonance lines, i.e., where the uranium absorbs most strongly. The considerations here presented show that the decrease in absorption is largest for the low energy resonances of U238 which are responsible for the bulk of the absorption in the case of uniform distribution. As a result, the resonance absorption of uranium lumps extends over a very large energy region–up to about 5000 ev. It can be decomposed, approximately, into two parts: the mass absorption, proportional to the number of U238 atoms present; and a surface absorption, proportional to the surface of the lump. The total decrease of the resonance absorption produced by lumping (the ``advantage factor'' of lumping) can be estimated to reach, under favorable conditions, a value as high as 20.
Effect of Geometry on Resonance Absorption of Neutrons by Uranium
Authors: Creutz E. , Jupnik H. , Snyder T. , Wigner E. P.
Published: April 2005

The total resonance absorption of neutrons by spheres of uranium and uranium oxide imbedded in graphite and bombarded with essentially a dE/E spectrum is found to be given by 1/α=c[1+(κ/ρR)] where α is the advantage factor, that is, the ratio of absorption of uranium when distributed uniformly throughout graphite to the absorption when it is lumped in a sphere. R is the radius of the sphere and ρ is its density. c and ρ were measured in various parts of a large graphite block exposed to cyclotron neutrons from the reaction Li (p,n). Values of c and ρ, respectively, are 0.051 and 5.1 g/cm2 for U3O8. In a newer notation, A = 10.9 barns and μ = 1.95 g/cm2.
Creep of Zinc Crystals
Authors: Tyndall E. P. T. , Artman R. A. , Wert C. A. , Eisner Robert
Published: April 2005

The plastic extension of zinc crystals in the region just beyond the elastic limit is found to obey the empirical law, η=btm in which η is the resolved shear strain, t is the time, m is a constant with a value close to 0.5 for initially unstrained crystals, and b is dependent on the resolved shear stress. Application of a theory due to Koehler shows that b should be related to stress (σ) in such a way that a plot of ln(mbσ2/Δσ) against 1/σ should be a straight line of slope −cG. In this, Δσ is the stress increment from one creep curve to the next, G is the shear modulus, and c is the concentration of anchor points which determines the lengths of segments of dislocation lines which generate according to the Frank-Read mechanism. The experiments are in fair agreement with this theory and values of c obtained are roughly equal to the concentrations of metallic impurities. The small amount of dissolved gases appears to play no significant part in the creep process.
Acceleration of Slender Bodies of Revolution through Sonic Velocity
Authors: Cole J. D.
Published: April 2005

The linearized theory of slender bodies in arbitrary motion at zero angle of attack has been worked out. The results have been applied to a smooth body accelerating uniformly through sonic velocity. The results theory can be used to estimate the nonlinear or transonic effects.

For an accelerating body, the parameter (bl/c2)½ is important where 2b = acceleration, 2l = length of body, c = sound speed at infinity. For sufficiently high (bl/c2)½, transonic effects can be neglected. Using linearized theory to estimate the ratio of nonlinear terms in the differential equation gives λ=nonlinear termssignificant linear terms=34(γ+1)δ2(bl/c2)12{log2δ2(c2bl)12−94},where δ = thickness ratio of body. The result above is evaluated at the maximum thickness of a symmetric parabolic arc body at the instant it passes through sonic velocity. For λ<1 transonic effects can be neglected while for λ>1 they begin to dominate. For practical applications the result shows that there is a possibility of a sufficiently long and slender missile accelerating fast enough to avoid transonic effects (e.g., 50 feet long, 5 percent thick, 3g acceleration). For conventional aircraft, transonic effects will dominate. An interesting side result is that when the acceleration is sufficiently large so that transonic effects do not matter the drag coefficient near sonic speed is independent of the acceleration (CD≐3δ2 for parabolic arc body).
Diffraction of Electromagnetic Waves by a Metallic Wedge of Acute Dihedral Angle
Authors: Grannemann W. W. , Watson R. B.
Published: April 2005

In the rigorous theory of diffraction by a conducting wedge as developed by Sommerfeld and extended by Pauli, the total field is represented by the terms given by geometrical optics plus a contour integral which represents the diffracted waves. If the faces of the wedge form a dihedral angle of π/m, m=1, 2, 3 … the contour integral vanishes identically and the solution given by geometrical optics is exact. This prediction has been tested and checked by measurements and calculations of the diffraction patterns of wedges whose dihedral angles were 90° and 30°. The measurements were made at a wavelength of 1.25 cm.
Re-Examination of the Nonsteady Theory of Jet Formation by Lined Cavity Charges
Authors: Eichelberger R. J.
Published: April 2005

A new type of analysis is applied to observations on jets from lined cavity charges in order to test the nonsteady-state hydrodynamic theory of a jet formation. The results support previous findings that the theory is qualitatively accurate, but give evidence of departures from the ideal situation assumed in the theory. An attempt is made to assess one of the more likely sources of error, the neglect of acceleration of the liner.
Relation to Diffusion Measurements of Some Beta-Ray Absorption Phenomena
Authors: Berkowitz A. E.
Published: April 2005

The absorption in thin layers of nickel, aluminum, and cobalt of beta rays from Co60 was measured in connection with the use of the surface counting method of determining diffusion coefficients. Data was obtained for foils and for evaporated and electroplated layers. In all cases the activity increased between 0 and 4 mg/cm2. A discrepancy was noted between the data for foils and those for evaporated and electroplated layers. It is shown that this general behavior is predicted by simple scattering and absorption expressions. The implications of these data for the use of the surface counting method are discussed.
Theory of Frequency Modulation Noise in Tubes Employing Phase Focusing
Authors: Stewart John L.
Published: April 2005

Oscillators employing phase focusing such as magnetrons have fairly well defined spokes whose rotational speed is proportional to the oscillation frequency. Each spoke is composed of a finite number of electrons having random velocities and consequently is subject to random fluctuations about a mean position. This spoke ``jitter'' leads to fluctuations in the oscillation frequency resulting in frequency modulation noise. It is the theoretical evaluation of the parameters of this noise as affecting the power spectrum of the oscillator output that is of interest here. The theoretical results compare favorably with the measured power spectrum of a voltage-tunable magnetron. The application of the formulas require an estimate of electron temperature although no attempt is made to evaluate this temperature. Amplitude fluctuation noise appears to be relatively unimportant in continuous-wave phase-focused oscillators.
Crystallization Kinetics in High Polymers. II. Polymer-Diluent Mixtures
Authors: Mandelkern Leo
Published: April 2005

The rates of crystallization of two polymer-diluent mixtures, poly-(ethylene oxide)-diphenyl ether and poly-(decamethylene adipate)-dimethyl formamide were studied at various temperatures ranging from 6° to 15° below the melting points of the mixtures. The various mixtures investigated encompassed a wide range of compositions; the volume fraction of the diluent v1 ranged from about 0.10 to 0.70. The crystallization behavior observed was strikingly similar to that previously reported for bulk polymers in the first paper of this series. The results are interpreted by making the necessary modifications to the treatment previously employed wherein steady-state nucleation and growth were assumed to occur simultaneously throughout the process. Agreement obtained between theory and experiment is similar to the corresponding results for the bulk polymer.
Orientation and Temperature Effects on the Electrical Resistivity of High-Purity Magnesium
Authors: Nichols James L.
Published: April 2005

The effect of crystal orientation on the electrical resistivity of high-purity magnesium at 24°C may be represented by the equation: ρ(φ)=4.60−0.75cos2φ, (in microhms/cm3),where θ is the angle between the hexagonal axis and the direction of current flow. The effect of temperature on the electrical resistivity for varying orientations shows temperature coefficients of 0.00390 and 0.00408/°C obtained perpendicular and parallel to the hexagonal axis, respectively, for the temperature range of 24° to 200°C. Magnesium shows rotational symmetry about the hexagonal axis with respect to electrical resistivity. Grain size has little or no effect on the electrical resistivity of magnesium.
``Gate Modulation'' of Electromagnetic Radiation
Authors: Lehovec Kurt
Published: April 2005

The space-charge layer at a p-n junction is a region of low concentration of electrons and holes, and therefore exhibits less absorption than the bulk of the semiconductor for radiation of sufficiently long wavelengths. Thus the space-charge region of a p-n junction provides an optical window of a width which can be modulated by an applied field. A quantitative estimate of this effect is given. Because of an obvious relation to unipolar transistors, the name ``gate modulation'' is proposed, as opposed to the ``injection modulation'' discussed previously.
Diffusion, Static Charges, and the Conduction of Electricity in Nonmetallic Solids by a Single Charge Carrier. I. Electric Charges in Plastics and Insulating Materials
Authors: Skinner Selby M.
Published: April 2005

The dynamic equilibrium of space charge in insulators such as ceramics, molecular crystals, or high polymers, is considered from the thermodynamic point of view with quantum-mechanical boundary conditions. The treatment constitutes the opposite extreme from the usual ohmic conduction equations; in the first paper, only the zero-current equilibrium of charge is considered. Applications are made to the observed charging of high polymers during molding.
Čerenkov Radiation of Electrons Moving Parallel to a Dielectric Boundary
Authors: Linhart J. G.
Published: April 2005

The phenomenon of Čerenkov radiations of electrons moving parallel to a dielectric boundary is investigated, using an eigenfunction expansion of the electromagnetic field. It is shown that the Čerenkov effect is similar to the excitation of surface waves in traveling wave tubes.
Silicon Solar Energy Converters
Authors: Prince M. B.
Published: April 2005

Theory is given for the design of silicon solar energy converters commonly known as the Bell Solar Battery. Values are given for the various parameters in the design theory. Experimental data are presented and compared with the theoretical relations based on a simple model.

It is found that with present techniques, units can be made with up to 6 percent efficiency in the conversion of solar radiant energy to electrical energy. An important factor in obtaining such high efficiencies is the reduction of the series resistance of the cell to as low a value as possible.
Signal-to-Noise Improvement and the Statistics of Track Populations
Authors: Wax Nelson
Published: April 2005

A treatment of the population statistics of signal and of noise patterns, or tracks, is given in this paper. Some idealized and abstract models of tracking procedures are studied; the models are intended to represent the processes encountered in radar tracking and in scanning nuclear emulsions for tracks. The equilibrium track population, the age distribution of the population at equilibrium, and a signal-to-noise improvement factor are obtained for each of the models considered. It is shown that the equilibrium population can be kept to reasonably small values, and the signal-to-noise ratio improved, if effective methods are used to eliminate deteriorating tracks.
Role of Positive Ions in High-Voltage Breakdown in Vacuum
Authors: Bourne H. C. , Cloud R. W. , Trump J. G.
Published: April 2005

Measurements were made of the electron emission from targets of magnesium, aluminum, steel, copper, gold, and lead when bombarded by ions from hydrogen, helium, nitrogen, xenon, and mercury. The ions, whose energy was varied over the range from 10 to 140 kilovolts, were produced by ionization of the residual gas in the anode electrode and emerged through a small opening into an essentially uniform accelerating field. An initial rapid rise of electron emission with ion energy was followed in all cases by a slow linear increase. The emission ratio varied from 2 to 20 and was maximum for nitrogen ions on steel. The effect of extractive gradient at the bombarded metal surface was slight and no simple dependence on the nature of the ion or of the bombarded metal was observed. The significance of these measurements on the electronion interaction theory of high-voltage breakdown in vacuum is discussed.
Nyquist's and Thevenin's Theorems Generalized for Nonreciprocal Linear Networks
Authors: Twiss R. Q.
Published: April 2005

It is shown that an N-node nonreciprocal linear network, with a system of internal thermal noise generators at temperature T, is equivalent to the source-free network together with a set of correlated nodal current generators, with infinite internal impedance, such that 〈iris*〉Avdν=2kT(yrs+ysr*)dν where yrs is an element of the network admittance matrix and ir is the rth nodal noise current with frequency v. The noise sources can also be represented by a system of nodal voltage generators, with infinite internal admittance, such that 〈vrvs*〉Avdν=2kT(zrs+zsr*)dν.

The application of these results to a system of coupled antennas in an equi-thermal enclosure is noted and necessary conditions for the realizability of passive nonreciprocal networks are derived.
Cross Correlation between Velocity and Current Fluctuations in Tube Noise
Authors: Yadavalli S. V.
Published: April 2005

In practice one calculates the noise figure of an electron device by the Rack-Llewellyn-Peterson method. In this method one uses the fluctuations in current and velocity at the entrance plane as the input quantities. In a procedure such as the above, one needs to know the correlation between the velocity and current fluctuations at the entrance plane. It is shown in this paper that such a correlation between the above fluctuations is zero under certain conditions.
Resonant-Cavity Field Measurements
Authors: Kitchen S. W. , Schelberg A. D.
Published: April 2005

The application of perturbation techniques to the quantitative measurement of both relative electric and relative magnetic fields in resonant cavities is described. The apparatus, procedures, advantages, and limitations are discussed, and the experimental results are compared with the calculable field distributions of a coaxial resonator. The theoretical shunt impedance and Q obtained empirically agree, respectively, within one and four percent of the calculated values.
Composition of the Interelectrode Prebreakdown Current in High Vacuum
Authors: Bourne Henry C.
Published: April 2005

Thermal rise measurements on vacuum-insulated electrodes subjected to steady gap voltages in the range of 80 to 100 kv show that the interelectrode prebreakdown current is composed chiefly of negatively charged particles. With aluminum electrodes the negative particles outnumber the positive particles (ions) by at least 300 to 1. With steel electrodes, the ratio is greater than 1000 to 1.
Interaction of Moving Charges with Wave Circuits
Authors: Pierce J. R.
Published: April 2005

When a charge moves along a nondispersive transmission line it induces forward and backward wave components in the line. For unaccelerated motion there is no radiation unless the charge moves with the speed of an unforced wave. For small accelerations, both radiation to the line and electromagnetic inertial effects caused by changes in the energy of the fields will be observed. The electromagnetic mass at velocities greater than the wave velocity is negative. Large accelerations can be handled by numerical computation. In the case of dispersive circuits, the charge radiates at frequencies for which the phase velocity of the circuit is equal to the velocity of the charge. This radiation is identified with Cherenkov radiation. Similar radiation takes place when a charge moves through a plasma.
Monte Carlo Calculation of Gamma-Ray Albedos of Concrete and Aluminum
Authors: Perkins J. F.
Published: April 2005

Number and energy gamma-ray albedos have been calculated for a material of Zeff=13, corresponding to both concrete and aluminum. The Monte Carlo method was used, the calculations being performed on an IBM-701. The single- and multiple-scattered components were evaluated separately; the multiple-scattered component was considerably the larger of the two in most cases, being as much as three times as large as the single-scattered component. For moderately small incident angles, the emergent photons are distributed approximately proportional to the cosine of the normal angle of emergence. The spectra peak around 150–250 kev and in some cases have a second peak at higher energy; such secondary peaks move upward in energy and increase in importance as the angle of incidence increases. The average energy of the emergent photons varies from 0.33 to 1.4 moc2. For the multiple-scattered component the average energy varies from 0.30 to 0.93 moc2. Buildup factors have been calculated for 2 moc2 gammas normally incident on aluminum of 2 and 4 mean free paths thickness.
Reverse Current and Carrier Lifetime as a Function of Temperature in Germanium Junction Diodes
Authors: Pell E. M.
Published: April 2005

The reverse current and carrier lifetime have been measured in a series of germanium diodes as a function of temperature between room temperature and liquid nitrogen temperature. The lifetime reaches a plateau at low temperatures, and its behavior can be explained in terms of the Hall-Shockley-Read recombination theory. Log iR vs 1/T exhibits a break to a shallower slope at lower temperatures, which can be explained in terms of charge generation by recombination centers in the space-charge region.
Transition Through a Contact Region
Authors: Hall J. G.
Published: April 2005

The one-dimensional contact region common to shock-tube flows is idealized by the simple model of initial step change in temperature and density at constant pressure. For weak transitions, neglect of pressure effects, and linearization of the conservation equations gives spatially monotonic temperature and density profiles with the contact region thickening as the square root of time. Experimental results are noted from shock-tube studies of two air/air contact regions. Insofar as comparison of theory and experiment is possible, the theory for weak transitions appears reasonable.
Short-Time Stress Relaxation Behavior of Plastics
Authors: Watson M. T. , Kennedy W. D. , Armstrong G. M.
Published: April 2005

An apparatus for measuring stress relaxation of plastics at constant strain in the time range of 0.01 to 2.5 sec after load application is described. Experimental results obtained indicate that rigid plastics at room temperature may be classified as either brittle or ductile. Brittle plastics sustain only low strains without fracture at the testing speed of the apparatus and undergo little relaxation of stress in this time range; ductile plastics sustain higher strains and undergo considerable relaxation of stress. The factors affecting relaxation behavior are briefly discussed. Increasing the strain, temperature, or plasticizer content generally increases the relaxation rate.

Many of the results yield a linear plot of stress vs logarithmic time, as has been reported in the literature for various materials tested at longer times. By application of one form of the Eyring absolute rate theory, an average free energy of activation for the relaxation process can be calculated. The value thus calculated for polymethyl methacrylate is in the range reported in the literature for other polymers.

An empirical measure of ``toughness'' can be based on these results. For many plastics this measurement is in accord with service performance.
Microwave Diffraction by Apertures of Various Shapes
Authors: Buchsbaum S. J. , Milne A. R. , Hogg D. C. , Bekefi G. , Woonton G. A.
Published: April 2005

Experimental results of the near zone diffraction field of circular and elliptical apertures and of the infinite slit are presented. The investigations were made on apertures which were illuminated by a plane polarized electromagnetic wave and whose characteristic dimensions were varied over a considerable range with respect to the wavelength of the incident radiation.

Most of the measurements are compared with predictions from recently published approximate theories and in a few cases with exact solutions. In general the agreement between theory and experiment is found to be satisfactory. Some of the discrepancies are discussed.
Electrical Breakdown in High Vacuum
Authors: Boyle W. S. , Kisliuk P. , Germer L. H.
Published: April 2005

Currents preceding breakdown have been measured between closely spaced tungsten electrodes in high vacuum. It is found that field emission currents sufficient to evaporate anode metal flow before breakdown. These currents follow the Fowler-Nordheim equation when field magnification due to surface irregularities on the cathode is taken into account. The field magnification is a function of distance at electrode separations less than 4×10−4 cm.

Explanation of the observed breakdown at low voltage and small spacing requires an unusually high yield of electrons at the cathode per ion formed in the gap. Furthermore there is no measurable direct enhancement of the current by ionization even at higher voltages. The high electron yield must therefore exist over the entire observed range of breakdown voltages. This high yield is satisfactorily accounted for by the increase in field emission due to the positive ion space charge, which in turn increases the positive ion current density until there is breakdown. It is shown that breakdown occurs when the field emission current is increased by only 65 percent. This condition is reached with the ion current density much smaller than the electron current density.
Theory of Non-Newtonian Flow. II. Solution System of High Polymers
Authors: Ree Taikyue , Eyring Henry
Published: April 2005

The authors' theory developed in the preceding paper I is applied to solutions of polystyrene, polyisobutylene, X-518 GR-S rubber, and lime base grease with good agreement with experiment. The parameters, xn/αn and βn (see the abstract of the paper I), were calculated, and are tabulated; these parameters are proportional to the surface concentration and the relaxation time of the nth group of flow units, respectively. The effects of the molecular weights of polymers, concentration, solvent, and temperature on these parameters were studied. Our results establish the following facts:

(1) The heterogeneity of flow units increases with increasing molecular weight.

(2) In the range of low concentration, βn (relaxation time) is independent of concentration, while the areal concentration of non-Newtonian units increases more rapidly than proportional to the bulk concentration of a polymer.

(3) A ``good'' solvent increases the concentration of non-Newtonian units, while the contrary is true for a ``poor'' solvent.

(4) In poor solvent solutions, the concentration of non-Newtonian units increases with increasing temperature, while the concentration is independent of temperature in good solvents.
Preliminary Results in Measuring Dynamic Compressibilities
Authors: Philippoff W. , Brodnyan J.
Published: April 2005

In order to supplement dynamic measurements in shear and bending, the vibration tester of the Franklin Institute Laboratories was used to measure the bulk compressibility of plastics using harmonic vibrations. Polyethylene and plasticized polyvinyl chloride were investigated. The values of the compressibility were comparable to the static values as far as they are known. A noticeable phase shift between pressure changes and volume changes could not be detected with certainty so that the bulk modulus B in dynes/cm2 is not a complex quantity. Especially for the polyethylene, a temperature range from −25 to +95°C and a frequency range from 0.0003 to 5 cps was used. The isothermals obtained could be shifted together using the method of reduced variables of Ferry. From the frequency shifts aT, an activation energy of 60 kcal/mole was obtained.
Study of the Kinetics of Ordering in the Alloy AuCu
Authors: Kuczynski G. C. , Hochman R. F. , Doyama M.
Published: April 2005

Ordering in the alloy AuCu was studied by measurements of the electrical resistivity as a function of time and temperature of ordering for samples disordered at various temperatures above the critical point. It has been established experimentally that the disordering temperature has a profound affect upon the rate of ordering. The higher the disordering temperature the faster is the rate of subsequent ordering. The dependence of the rate of ordering on the ordering temperature seems to indicate that the transformation is nucleated even at very low temperatures. The appearance of a twin-like structure during the disorder-to-order transformation has also been studied as a function of the previously mentioned variables.
Analysis of Electrode Phenomena in the High-Current Arc
Authors: Cobine J. D. , Burger E. E.
Published: April 2005

An analysis is made of the phenomena at the electrodes of a high-current short-time arc. It is shown that the input power density to the anode spot is in the range 5×104 to 1×106 watts/cm2. To a first-order approximation, all this power can be carried off by evaporation. Power conducted into the metal and lost by radiation is negligible in the probable operating range. For most materials, the anode spot is probably considerably above the boiling temperature. The process of evaporation holds the spot temperature constant at a value such that the input power and evaporation power are equal. Experimental data indicate that for any given metal the anode spot temperature is that for which the evaporation power density is at least 3×105 watts/cm2. As an example, for copper the theoretical limits of temperature are 2490 to 3040°K, while experimental data indicate a temperature of 2920°K. Other metals considered are: Ag, Al, C, Fe, Mo, Sn, Ti, W, Zn, Zr. It is also shown that for the maximum power input that can be expected at the cathode, the thermionic emission current density is very small compared to the observed values of current density.
Submicroscopic Structure Determination by Long Wavelength X-Ray Diffraction
Authors: Henke Burton L. , DuMond Jesse W. M.
Published: April 2005

This paper reviews the theory of low angle x-ray diffraction as applied in the long wavelength region for the determination of particle sizes and shapes and other structural features in the submicroscopic size range and emphasizes the advantages to be gained by employing the longer x-ray wavelengths (8 to 25 A). It also is intended to serve as an introduction to a description of an entirely new instrumental technique developed for this long wavelength range utilizing a diffraction apparatus consisting of a special gas-filled x-ray tube and a total reflection camera in which the primary radiation is simultaneously monochromatized and made to converge to a point focus. The sample for study is placed in the converging part of the primary beam and the diffraction patterns are formed around the point focus on a photographic film.
Photoelectric Work Functions of the Borides of Lanthanum, Praseodymium, and Neodymium
Authors: Decker Richard W. , Stebbins Dean W.
Published: April 2005

The DuBridge variation of the Fowler theory of photoelectric emission was utilized to determine the work function of the borides of La, Pr, and Nd. The work functions of LaB6, PrB6, and NdB6 were found to be 2.74 ev, 3.12 ev, and 4.57 ev, respectively.
Influence of Space Charge on the Potential Distribution in Mass Spectrometer Ion Sources
Authors: Brubaker W. M.
Published: April 2005

The role of space charge as a factor influencing the potentials and potential gradients in a mass spectrometer ion source of the electron bombardment type is calculated. Planar equipotential surfaces are assumed, and the analysis then becomes that of a plane parallel positive ion diode. The ``cathode'' of the ion diode may be either emission-limited or space-charged-limited. The analysis considers the charge of the electrons in the ionizing sheet and the charge of the positive ions in the diode.

At a critical gas pressure the influences of the positive and negative charges on the potential of the ionizing region are equal and opposite, for small ionizing current. This concept leads to a pressure normalization in terms of the critical pressure. For a given source geometry and electron bombarding energy one can construct universal curves which give the potentials and the potential gradients as a function of the normalized gas pressure and the ratio of the ionizing electron current density to the repeller voltage. Experimental data are in agreement with the predictions of the theory.
Rectification Properties of Metal Semiconductor Contacts
Authors: Borneman E. H. , Schwarz R. F. , Stickler J. J.
Published: April 2005

Metal semiconductor contacts of a number of different metals were made on n- and p-type germanium using jet etching and plating techniques. Current voltage curves taken on 12 of these metals on 5 ohm-cm n-type germanium showed rectification which follows the diode equation J=J0(eqV/kT−1). No correlation was found between the reverse saturation current densities of these diodes and such properties of the metals as work function, electromotive force, etc. For those metal contacts possessing the lowest saturation current densities, calculations indicated the current crossing the contact was to a large percent hole current and that the magnitude of the hole current was controlled primarily by the geometry of the diode. All metals plated on 5 ohm-cm p-type germanium produced ohmic contacts of resistivity comparable to the spreading resistance expected for the diode geometry used.

For indium diodes, a study of rectification versus resistivity indicated that the barrier produced on both n- and p-type germanium with plated contacts is one to electron flow rather than hole flow. When the assumption of only hole current crossing the barrier was made, it was shown that the I–V curves calculated from the diode theory, for different resistivities of germanium, were in qualitative agreement with the measured curves. Curves of zero voltage conductance versus temperature for different resistivities of germanium were also found to be in good agreement with those calculated on the assumption of all hole current.
Plasma Oscillations in Electron Beams
Authors: Hernqvist K. G.
Published: April 2005

Self-sustained ion and electron plasma oscillations have been observed simultaneously in an ion neutralized electron beam traveling in a transverse magnetic field. The observed frequencies of oscillation agree with the Langmuir-Tonks theory for plasma oscillations. Electron plasma oscillations occur when the electron plasma frequency equals the gyro frequency of a circular orbit in the magnetic field.
Power Flow in Electron Beams
Authors: Walker L. R.
Published: April 2005

The ac power flow in an electron beam moving in weak electric fields is given a precise definition. Since it is a quantity quadratic in the applied field strength its evaluation requires the quadratic perturbation theory of the beam to be worked out. Quadratic expressions in the first-order variables of the beam and circuit may also be written down which have the dimensions of power and are shown to satisfy a conservation theorem. The relations between the exact quantities of the nonlinear theory and the constructs from linear theory are discussed.
On the Space-Charge-Limited Current between Nonsymmetrical Electrodes
Authors: O'Neill George D.
Published: April 2005

The validity of employing an equivalent symmetrical anode for expressing the space-charge-limited current between nonsymmetrical electrodes is examined. It is shown that when the equivalent anode is determined by the capacitance, the error in the expression for the current is usually quite small and its approximate magnitude may often be anticipated. Exact expressions for the capacitance of some basic electrode arrangements are given, followed by a brief resumé of corrections required for interpretation of experimental data.