bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coaxial Ferrite Phase Shifter for High Power Applications
Authors: Boxer A. S. , McCarter R. S. 
Published: April 2005

The low- and high-power behavior of a coaxial ferrite-loaded transmission line has been studied experimentally at microwave frequencies. Longitudinal magnetic biasing fields both above and below the cutoff range (ω/γ−4πMs≤Hdc≤ω/γ) were explored, the two regions yielding devices with markedly different characteristics. The mechanical structure consisted of a rigid ⅞-in. coaxial line fully loaded with Trans-Tech 1–103 ferrite together with appropriate quarter-wave dielectric transformers.
(1) Operation below cutoff (0≤Hdc&lt;ω/γ−4πMs), f=3080 Mc: These parameters permit construction of a compact, light-weight phase shifter producing 360° of phase shift in 10 in. of active length upon application of only 100 oe. Approximate values for hcrit are determined from the measured threshold powers and plotted versus applied field.
(2) Operation above resonance (Hdc&gt;ω/γ), f=1350 Mc: With these parameters, a device can be built that is capable of handling at least several hundred kilowatts of rf peak power while maintaining a figure of merit of 1000 or more. The loaded coaxial line provides 360° of phase shift in 24 in. of active length when biased from 950 to 1350 oe. The high-power and loss characteristics of the latter device permit application to electronic steering of the transmitter beam in a linear array antenna where relatively few phase shifters suffice. The low-field device is suited for beam control in a planar array where large numbers of relatively small phase shifters of medium peak-power capability are needed.
Slow-Wave uhf Ferrite Phase Shifters
Authors: Sakiotis N. G. , Allen D. E. 
Published: April 2005

A brief general discussion of the loss mechanisms of ferrites and garnets is given. An idealized representation of the absorption loss as a function of frequency and the applied magnetic field is utilized to define five distinct regions within which devices using ferrimagnetic materials may be operated with low absorption loss.
Slow-wave transmission lines for uhf frequencies are discussed, and the observed phase shifts per unit length for these and a conventional transmission line are given.
It is concluded that through the use of slow-wave transmission lines phase shifters can be designed at uhf frequencies which require as little as one-fourth the length required by a conventional transmission line.
Waveform of the Time Rate of Change of Total Flux for Minimum Core Loss
Authors: Schenk H. L. , Young F. J. 
Published: April 2005

In testing magnetic materials core losses are measured when the time rate of change of total flux dφ/dt in the core varies sinusoidally. Although it may seem intuitive that the core loss for a given flux density is a minimum when dφ/dt is sinusoidal, measurements and a simple analysis indicate otherwise. It is shown that the core loss is smaller if the time rate of change of total flux in the core follows a square wave than it would be if the time rate of change of total flux followed a sine wave, with the peak induction being the same in both cases. By a variational method the ratio of square-wave to sine-wave eddy current losses for a given value of peak flux density is found to be 8/π2.
The ratio of square-wave to sine-wave core losses is measured as a function of induction for a fixed frequency and as a function of frequency for a fixed induction using a Hipersil specimen (cube-on-edge orientation). A feedback circuit is used to prevent distortion in the waveform. When the measurement is made at 60 cps the ratio is about 0.90 for flux densities below 12.5 kgauss and rises with increasing flux density to about 0.96 at 17.5 kgauss. For an induction of 5 kgauss the ratio decreases from about 0.92 at 30 cps to 0.87 at 120 cps.
Low-Frequency Losses and Domain Boundary Movements in Silicon Iron
Authors: Wycklendt Daniel A. 
Published: April 2005

Earlier observations of very low-frequency losses in (110) [001] textured silicon iron have been extended to include losses produced by excitation with a sinusoidal field intensity. Excitation frequencies of 0.005 to 10 cps and flux density amplitudes of 10, 15, and 17 kgauss were used in these measurements. The downward concavity of the loss-frequency curve near zero frequency, previously reported for sinusoidal induction, is greatly exaggerated by imposition of a sinusoidal field intensity.
To further investigate these low frequency loss anomalies, low-amplitude, high-frequency fields were impressed on the material during cyclic magnetization at low frequencies. The superposed field, most often of 320- or 1000-cps frequency, had an amplitude considerably smaller than the coercive force of the material. Waveforms of the gross, low-frequency magnetization and the incremental, high-frequency magnetization were accurately controlled by high-gain, direct-coupled, feedback amplifiers. The ratio of the Ḃ amplitude to the H amplitude for the high-frequency components varied greatly within a cycle of magnetization. |Ḃh|/|Hh| was also found to vary with the peak value and waveform of the gross induction. Most significantly, the ratio increased greatly with frequency of the gross magnetization at very low frequencies. These changes can be attributed to an increase in the number of domain walls in simultaneous motion when the speed of gross magnetization is increased.
Magnetic Properties of Cr5S6 in Chromium Sulfides
Authors: Dwight K. , Germann R. W. , Menyuk N. , Wold A. 
Published: April 2005

Several samples of CrSx with 1.145&lt;x&lt;1.200 were carefully prepared and chemically analyzed. The expected crystal structures were verified by x-ray analysis, which failed to indicate the presence of any impurities. Conductivity measurements indicated the existence of metallic conductivity in these samples between 77° and 300°K. Magnetic measurements supported the suggestion that the ferrimagnetism of CrSx materials arises from the presence of the Cr5S6 phase.
The magnetization curves for x=1.194 demonstrated the following salient properties of the Cr5S6 phase: a ferrimagnetic Curie point of 305°K, a peak magnetization of 6.9 emu/gm in an external field of 8500 oe, a ferrimagnetic-antiferromagnetic transition over a 5° temperature interval, a transition temperature in the neighborhood of 158°K which is subject both to thermal hysteresis and to shifting by an external magnetic field, and an antiferromagnetic susceptibility below this transition. The transition temperature, as well as the peak magnetization, decreases with increasing chromium content. A simple model is tentatively proposed, and appears to be consistent with the observed behavior.
An Analysis of the Maser Oscillator Equations
Authors: Sinnett D. M. 
Published: April 2005

This paper analyses the maser oscillator equations which describe the interaction between the resonant cavity and the inverted population of the electron spin system of the paramagnetic substance. It is shown that these equations will not allow periodic solutions thus refuting the theory, based on computer solutions, that this interaction is responsible for the pulsed mode of operation of the oscillator.
Characteristics of solutions of these equations are determined analytically, and the ambiguity of computer solutions is discussed with the aid of examples. Numerical solutions are presented which show that periodic solutions may be induced by supplementing the spin system equation with an additional term.
Magnetic Field Reversal by Relativistic Electrons Which Slow Down While Circulating in a Uniform Impressed Magnetic Field
Authors: Tonks Lewi 
Published: April 2005

The prior restriction to conservative motion of the electrons has been removed, but scattering has still been neglected. The rate of energy loss has been used to derive the stationary distribution over a range of energy (or momentum) and canonical angular momentum for an arbitrary magnetic field distribution. A necessary ingredient is the retardation of the electrons; the radiative component of this has been estimated, but not included; the dynamical friction component, arising from motion through a uniform, fully ionized plasma, has been used as the sole contributor to energy loss. This friction also affects the canonical angular momentum and the latter's change in one cycle relative to the energy change has been formulated. Maxwell's equation connecting magnetic field with current density, applied to the stationary distribution, has permitted the formulation of the relation between field and the other variables. This completes the number of relations required to determine the magnetic field (eigenfunction) arising from a given rate of electron injection (eigenvalue): The trajectory equations have been derived.
It has been necessary to picture physically the complete evolution of a trajectory from injection to stopping, both to understand what the mathematics says and to devise an adequate machine program. When field reversal occurs, then just before the electrons die, the electron swarm divides into two counter-rotating eddies. Two iterative solution techniques have been used to calculate the field distributions for a range of initial energies, field strengths, and injection rates. A striking result is that once reversal of field occurs by increasing the injection rate, it is generally true that the reversed field varies little, but the layer becomes progressively thinner as the injection rate increases further. At some rate the layer thickness passes through zero and thereafter the injection radius lies not at the apocenter of the initial trajectory but at the pericenter, the layer protruding from its prior position.
For full-energy radii of gyration which are less than about one-third the injection radius, anomaolus solutions appear which are unstable. A number of aspects of the problem of incorporating an E layer into a thermonuclear device are briefly discussed, namely, the effect of scattering, the possibility of two-beam instability, the injection of the electrons, effects of end reflection in a finite-length layer, electrodynamic effects, and plasma diamagnetism.
Theory of Dislocation Mobility in Pure Slip
Authors: Lothe Jens 
Published: April 2005

The mobility during glide of uniformly moving dislocations or dislocation segments supposed not to be obstructed by any Peierls' barrier is estimated. For a straight freely moving dislocation, the strong anharmonicities in the core region, the thermoelastic (edge dislocation) and the phonon viscosity effect give rise to a drag stress at ordinary temperatures T∼θ, θ being the Debye temperature, of the order σ∼110ε×V/c in insulators. In metals the thermoelastic effect is negligible, while the core anharmonicity effect and the phonon viscosity effect will be of the same order of magnitude as in insulators. In the above formula, ε=thermal energy density, V=dislocation velocity, and c=velocity of shear waves. The scattering of phonons by the dislocation also causes a drag stress at ordinary temperatures of the order of magnitude of the above formula.
All of the above mentioned contributions to the drag stress go rapidly to zero with decreasing temperature. However, if the dislocation is constrained by the Peierls' barrier except at freely moving kinks, the kink mobility determines the dislocation mobility. It is shown that the scattering of phonons of a half-wavelength longer than the kink width causes a drag stress which may outweigh all other contributions up to ordinary temperatures, and which persists with decreasing temperature as T down to a temperature ∼θb/D, where b=the lattice spacing constant and D is the kink width.
Some Electrical Properties of the Porous Graphite Contact on p-Type Silicon
Authors: Harman George G. , Higier Theodore , Meyer Owen L. 
Published: April 2005

Some unusual properties of the porous graphite contact on p-type silicon are described. Current through the sample reaches a saturation level that is inversely proportional to the amount of adhered water vapor. Other gases such as ammonia, H2S, and HCl modify the shape or amplitude of the saturation current. There is a hysteresis loop in the low voltage region which is similar in appearance to that of a ferroelectric. The general method of measurement can be applied to studying the semiconductor surface as well as the contact phenomena. The possible applications include such devices as current regulators, humidity detectors, and surface-barrier radiation detectors.
An electronic band model, which includes a trap-dominated inversion layer, is presented to explain the phenomena. This model also integrates various conflicting theories of metal-semiconductor contacts.
Effect of Compton Scatterings by Air Molecules on the Sharpness of a Beam of Gamma Rays
Authors: Robinson Lawrence Baylor 
Published: April 2005

A special problem involving the passage of a beam of gamma rays through air is examined. The effect of Compton scatterings on the sharpness of the gamma-ray beam is discussed. Other mechanisms whereby the beam is softened are not included because the interest is only in the component of the beam which suffers little energy loss.
The problem of interest is similar, in some respects, to multiple scattering of electrons with negligible energy loss. The mathematical expression for the collision process is different, however. A method used by Fermi in regard to multiple scattering of electrons is also used here. The Klein-Nishina cross section for Compton scatterings is introduced into the present problem in order to obtain scattering probabilities.
Some numerical results are obtained which can be applied to cobalt-60 gamma rays. The results are presented in graphical form.
An Electromechanical Effect in Semiconductors
Authors: Westbrook J. H. , Gilman J. J. 
Published: April 2005

The resistance of semiconducting crystals to indentation deformation has been found to be lowered significantly (up to 60%) by the simultaneous presence of a small potential (0.05 to 10 V) between the indenter and the crystal surface. This electromechanical effect appears to be confined to the plastic strain region of a surface layer of material 2–3 μ deep.
A large body of experiments of varied nature have established that the effect is real and not spurious. Similar effects are observed in a number of different semiconductors (Ge, Si, InSb and SiC) but not in metals or ionic crystals. The effect disappears at elevated temperatures but becomes enhanced below room temperature. It is not sensitive to the type of current carrier. The roles of surface preparation, crystallographic orientation, kind and concentration of charge carrier, geometry, and time have also been examined. Other and possibly related experiments show significant enhancement of the surface photovoltage (the Dember potential) by a longitudinal electric field. All of these experiments are extensively documented and discussed but no satisfactory model or mechanism has yet been conceived.
Diffusion, Solubility, and Electrical Behavior of Li in GaAs Single Crystals
Authors: Fuller C. S. , Wolfstirn K. B. 
Published: April 2005

The solubility, diffusion, and electrical behavior of Li in GaAs have been investigated by means of chemical analysis, conductivity, and Hall-effect measurements. Both floating-zone and Bridgman crystals have been examined.
The solubility of Li in GaAs from the equilibrium surface alloys has been determined from 500° to 1150°C. A maximum solubility of 4×1019 Li cm−3 occurs at about 1050°C. Solubilities from surface Li2O and gaseous LiBr have also been determined over limited temperature ranges.
Li diffusion has been followed by electrical and chemical methods. The diffusion is nonideal and follows the relation, D*=0.53 exp(−1.0/kT), where D* is the apparent diffusion coefficient. Li produces ``automatic'' compensation of GaAs. Out-diffusion of Li results in acceptor formation. This behavior has been examined in detail and interpreted by postulating initial formation of stable (Li+Li=) doublets which, through the hole-electron equilibrium, cause Li to dissolve as Li+ donors to near compensation.
A marked effect of donor doping on the solubility of Li has been found.
Certain unexplained differences between crystals exist which are being further investigated.
Electron Optical Investigation of Thin Films of Lithium on Tantalum, Platinum, and Carbon Substrates
Authors: Esquivel A. L. , Fung Ai-Chun , Rhoads H. U. , Weber A. H. 
Published: April 2005

Thin films of lithium when evaporated onto well-polished, chemically cleaned, and outgassed Ta and Pt substrates formed uniformly thick layers (in the range 240–1600 Å) suitable for the p-n reaction in the Van de Graaff generator. A thin carbon coating, (about 300 Å thick) evaporated upon the Li film from a heated carbon filament immediately following the deposition of lithium on Ta and Pt substrates, insulated chemically the lithium from the air with its water vapor content and also provided carbon replicas of the Li films surface for electron microscopy.
Proton bombardment of the carbon-coated Li films had no visible effect on the carbon coating nor on the Ta or Pt substrate. However, after a proton beam bombardment of 10 μA-min at 1.88 MeV, the Li films gave evidence of some initial damage effect (growth of grain size plus surface unevenness) which appeared to anneal away with subsequent bombardment.
Orientation effects were observed in Li films deposited upon carbon substrates (in turn deposited on nickel lectromesh grids) in a special evaporator, attached to and forming a part of the vacuum system of the electron microscope (RCA type EMU-2B) in order to avoid contamination of the Li with the laboratory atmosphere. Electron diffraction patterns revealed the following: (1) random orientation for the thinner (240 Å, approximately) Li films and (2) preferred orientation of the (110) and (200) planes nearly perpendicular to the surface for the thicker (1600 Å, approximately) films.
Use of Modified Free Energy Theorems to Predict Equilibrium Growing and Etching Shapes
Authors: Jaccodine R. J. 
Published: April 2005

This paper offers a construction that gives the limiting or ``equilibrium'' shape of an etching crystal. The conditions for hillock and pit stability and face rounding are also obtained.
Experimentally, germanium cylinders with different zone axes were etched to develop ``equilibrium cross sections.'' These were in good agreement with the construction. Other uses of the construction are discussed.
Single, Temperature-Dependent Stress-Strain Law for the Dynamic Plastic Deformation of Annealed Face-Centered Cubic Metals
Authors: Bell James F. 
Published: April 2005

Large amplitude wave propagation in annealed aluminum is studied experimentally to within 70°C of the melting point of the metal. The strain-rate-independent, finite amplitude wave theory is found to apply at all temperatures. The governing stress-strain law in each instance is parabolic. The coefficient of the parabolic stress-strain law varies linearly with the absolute temperature.
The annealed, face-centered cubic metals of aluminum, copper, lead, gold, and silver are all found to have the same parabolic stress-strain law at absolute zero.
Thus, from experiments using the author's diffraction grating technique, a single stress-strain law is found which is applicable at any temperature to any of these annealed metals whose melting point is specified.
Effect of a Small Stokes Shift on the Operation of Three-Level Masers
Authors: Warter Peter J. 
Published: April 2005

Small differences between the emission and absorption spectra of three-level maser centers can have a pronounced effect on maser operation. This paper considers the effects of a Stokes shift, the simplest and most probable difference. If there is a Stokes shift which is large compared to the linewidth, the operation of the maser will be essentially four level. If there is a small Stokes shift (some fraction of the linewidth) the operation will still be three level, but the Stokes shift will significantly affect the operation of the maser. The principal effects will be a shift of the maser line from the peak in the fluorescent emission line (away from the absorption peak) and a reduction in the upper level population required to reach the threshold of oscillation.
The evidence is not conclusive as to whether there is a Stokes shift in the ruby R1 line, but if there is a shift it is at most a small fraction of the fluorescent linewidth at room temperature. Shifts of the ruby maser line to the red have been observed by D'Haenens and Asawa and have been attributed to large temperature changes. It is likely that the temperature shift, while important, will not explain the shift which has been observed. Gires and Mayer have found the lower state population of an operating ruby maser to be approximately 75% of the unexcited population rather than approximately 50% and have suggested a Stokes shift as a possible cause of the reduction in the upper state population at threshold. This paper considers the effect of such a small Stokes shift on the operation of an otherwise ideal three-level maser.
Nonlinear rf Behavior of Electron Beams with Velocity Distribution. II. Application to Rectangular Velocity Distribution
Authors: Mihran T. G. , Yu S. P. 
Published: April 2005

The nonlinear disk electron analysis in Part I is applied to a practical example. Two changes are imposed on the analysis to decrease the computer running time. Electron trajectories and the first three components of current are calculated for a beam with a rectangular velocity distribution that is simulated by eight dc velocity classes. Excellent agreement is obtained with a linear theory for small values of initial density modulation. Periodic variation of the space-charge parameter leads to the equivalent of scalloped beam amplification in a multivelocity beam.
A linear force-taper correction is derived and its stabilizing effect is shown. Its use is suggested for improving the accuracy of monovelocity disk electron calculations.
The interpretation of space-charge wave decay in multivelocity electron beams as spatial Landau damping of the fast wave is questioned. It is suggested that damping is due to multidimensional effects not taken into account by present linear and nonlinear one-dimensional theories.
Microplasma Breakdown in Germanium
Authors: Poleshuk M. , Dowling P. H. 
Published: April 2005

Interpretation of breakdown results in Ge diodes is frequently complicated by effects associated with surface excess current. When these effects are minimized, breakdown is observed within the junction at a ``breakdown center,'' starting at a definite voltage VB, and is accompanied by the onset of microplasma pulses. In any one diode, there may be a number of centers, each having its characteristic value of VB and producing characteristic microplasma pulses. The minimum value of VB determines the breakdown voltage of the diode and it is possible to increase the latter radically by etching away centers having lower values of VB.
Observations were made at temperatures from −253° to 27°C on Ge alloy junctions (n-type base resistivities from 0.54 to 5.4 Ω-cm). The properties of the pulses are discussed in some detail: the effect of raising the voltage above VB, the effect of light, and the temperature coefficient of VB. Values of the last are sufficiently high to suggest that suitable diodes can be used as cryogenic thermometers capable of reading smaller changes than 0.01°C at −253°C.
Various aspects of the microplasma breakdown are discussed: the mechanism for triggering a pulse and that for ``turning it off,'' the role of the spreading resistance, the possible role of a negative resistance at breakdown, and the effect of microplasma breakdown on the measurement of carrier multiplication at voltages in the vicinity of breakdown.