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A computer program has been written to produce pole figures using the data from an x‐ray texture goniometer. The data are corrected for background and absorption. The pole figure is also stored on magnetic or paper tape in a form suitable for quantitative calculations. As an example, the Hall coefficient of a poly‐crystalline sample of a close‐packed hexagonal material is computed from the pole figure of the sample in terms of the single‐crystal components of the Hall tensor.

Two scanning techniques are now being used to determine the vibrational patterns and far‐field sound radiation of complex vibratory systems. One technique is a near‐field scanning apparatus which scans the vibrator and gives a three‐dimensional display on graph paper of the nodal patterns. The other scanning technique uses the principles of holography to locate far‐field sound sources on the vibrator. These two methods, coupled together, have demonstrated a unique capability to locate acoustic sources and hot spots on vibratory systems.

The dielectric constant and permeability of a metallic‐obstacle medium are obtained in this paper by various static methods. The equivalent shunt capacitive susceptance and series inductive reactance of the individual obstacles are also determined. In the first part of the paper, a correspondence is established between an infinitely thin conducting obstacle and an aperture in an infinitely thin conducting wall. With the aid of this correspondence, delay medium formulas are given for several obstacle shapes. Formulas are then derived for the effect on the magnetic field of moderate obstacle thickness. Finally, it is shown how the electric and magnetic constants may be evaluated by electrolytic tank measurements in the case of obstacles having completely arbitrary shape and thickness. This has been done for a typical delay medium, and the effect of obstacle thickness on the index of refraction is shown.

The paper deals with the utilization of electron mirror microscopy for pictorial representation of the distribution of electrical conductivity. Previously described conductivity pictures obtained by this novel kind of electron microscopy have been of the normal two‐dimensional type; this paper reports three‐dimensional display of conductivity distributions. It discusses the concept of ``stereo‐micrographs of conductivity.'' It is shown that a three‐dimensional display of the conductivity distribution of thin films is possible by combining two electron mirror micrographs to a stereo‐pair. The two micrographs are distinguished solely by the amount of current passing through the specimen. As experimental evidence of the feasibility of three‐dimensional ``conductivity pictures'' a stereo‐micrograph of a test sample with artificially prepared areas of different conductivities is shown. Limitations and precautions to be observed are briefly discussed.

Electric fields associated with the space‐charge layer at the surface of silver halide grains are expected to have a marked effect on the photographic properties of emulsions. The purpose of this paper is to describe a new method based on dielectric measurements to obtain information on the surface layers. It is shown that the surface layers have a strong effect on the low‐frequency dielectric constant so that it is possible to derive the properties of the former from measurements made on the latter. Formulas connecting the layer properties to the dielectric constant of the crystal are derived. The experimental results, obtained with the method described here, will be the subject of a separate paper.

Electron mirror microscopy is a rather novel research instrument. It has recently been demonstrated that it can provide micrographs not only of the relief structure of a specimen but also of such purely electrical properties as contact potentials, conductivities, surface charges, and even space charges. This paper deals with the feasibility of electron mirror microscopy for pictorial representation of magnetic properties in general, and of magnetic domain patterns in particular. It is shown that electron mirror microscopy is actually a feasible and independent method for electronically depicting magnetic patterns. The section of the paper dealing with experimental work begins with magnetic specimens of artificial nature, e.g., a recorder head, containing one or more linear magnetic dipole stray fields which are controllable. After establishing the basic facts of magnetic contrast formation with this type specimen, the paper reports on experiments conducted with specimens of barium ferrite and nickel ferri...

All possible linear electro‐optic retardation schemes for the twenty classes of linear electro‐optic crystals are synthesized in this paper under the single condition that light does not split directionally in a crystal. The result of this synthesis is tabulated in Table II. It gives the retardation and permissible polarization formulas for each class of crystals. It, therefore, may be used as a guide for designing linear electro‐optic devices. As an example, a linear transverse scheme for class 42m crystals (KDP, ADP) is selected from this table and verified experimentally. In this scheme, light is along (110) and electric field is along (001). This particular scheme has as advantages: no need for transparent electrodes and that the induced retardation can be increased by increasing the length‐to‐width ratio of the crystal. Table II depicts also the variations of retardation and permissible polarizations as the direction of light and electric field change under the above condition. This provides the reader with a foundation for synthesizing the electro‐optic‐polarization modulation and single‐side‐band‐suppressed‐carrier modulation (SSBSC). Again, as an example, a new scheme using cubic crystals for single‐side‐band and/or SSBSC modulation is proposed in this paper.

From experiments dealing with electrical breakdown phenomena in vacuum, it is clear that at voltages below that level actually required to produce breakdown, there occurs a low‐level electron emission from highly localized regions of the cathode surface. This paper illustrates a technique for measuring the dependence of current upon voltage from one such region, utilizing variations in brightness of a phosphor screen. The technique avoids the possible confusion of a total current measurement which can result from the presence of simultaneously emitting areas or which can result from emission from regions of the electrode structure whose contribution to total current is unsuspected. This paper further demonstrates a method for the detailed location of particular emitting areas on the electrode surface. The procedure involves as a first step, the determination of the approximate location of the emitting region of interest using a phosphor screen. Following this, the electrode under study is used as a cathod...

The fabrication of a planar guard ring diode which exhibits uniform microplasma‐free breakdown is described. Discrepancies are discussed between the behavior of these junctions and those reported by Batdorf et al. and Chynoweth, including results showing extremely hard V‐I characteristics associated with uniform avalanche breakdown. Experimental evidence is presented which confirms Shockley's theory in which the breakdown behavior is predicted from the Poisson distribution of impurities within the space‐charge layer. The photomultiplication technique as described in Paper I is applied to uniform p—n junctions. The linearity of 1/M vs V, as predicted by theory, was verified for values of M between 1.6 and 500. For higher values, the multiplication curves deviate from a straight line. In this higher range they are in good agreement with the pulse‐multiplication model developed in Paper I. Light emission patterns from these junctions are shown and a correlation between these patterns and crystal properties is discussed. The effects of resistivity striations in the silicon single crystals is shown to have a strong effect on breakdown areas and no effects of dislocations and oxygen on uniformity are found. From capacity and multiplication measurements a value for the breakdown field of EB=445±25 kV/cm was obtained for a 32‐V junction.

Two techniques of radiography by means of secondary photoelectrons liberated by hard x‐rays (180 kv), one by reflection and one by transmission, are described. Special fine‐grained photographic emulsions of the Lippmann type are required which will not be affected by x‐rays traversing the film, but are sensitive to photoelectrons liberated from the surface of a specimen in intimate contact with the photographic film or paper. In this way photographic negatives may be reproduced (from the silver of the image), microradiographs prepared by enlargement of any area of the radiograph, surface topography studied, ores analyzed, etc. For electronic radiography by transmission, instead of the specimen being its own electron generator, a thin metal foil (usually lead) pressed against the specimen generates the electrons which then traverse the thin specimens, and register on the photographic film or paper. Applications are papers, insect wings, varnish or rubber films, plant leaves, tissue sections, plastics, and alloys.

An optical technique, reported in a previous paper, has been used to measure surface oscillations on a series of thick 5.5‐in. diam steel plates of different thicknesses while they deform under explosive attack. Data obtained from the four 1025 steel specimens illustrated in the previous paper, and data obtained from two additional specimens have been analyzed partially. Results are compared with predictions from the theory of elasticity for the case of a diverging pulse. Elementary theory, known to be incorrect in the physical regime studied, is shown to give many satisfactory predictions for large distances from the charge.

In this paper the applicability of non‐radiating surface waves for transmission lines is investigated. Two types of waves are considered. The first one, originally studied by A. Sommerfeld, is guided by a cylindrical conductor of finite conductivity. Although this wave type has (under comparable conditions) much lower attenuation than the waves in coaxial cables or rigid wave guides, its practical application is restricted by the fact that the extension of the field is very large. Efficient excitation and undisturbed propagation of this wave mode are feasible only for very high frequencies. The other wave type considered in this paper has not been treated in the literature. It is guided by a conductor which is coated with a dielectric layer or the surface of which is otherwise modified; for example, by being threaded. The field of this wave type has a structure similar to that of Sommerfeld's wave, but the extension of the field can be controlled by the surface modification. Thus low loss transmission lines on the basis of this wave type become feasible for frequencies above 100 megacycles. The information necessary for the design of such lines is given and the agreement between the theoretically expected transmission losses and the measured transmission losses is checked.

The principal aim of this paper is to develop the theoretical and computational procedures used in the following paper. The Eikonal theory of crystal diffraction is summarized, and the computational procedures for obtaining the ray trajectory and the phase change along the ray in distorted crystals are described. Specifically, the x‐ray diffraction theory is applied to the analysis of dynamical diffraction effects observed by x‐ray topography at the edge of a thin oxide film superposed on a silicon host crystal. The critical importance of symmetry properties of topographs in evaluating the computational procedures is emphasized. The present computational procedures are quite general and can be used with appropriate modifications for a quantitative understanding of diffraction effects, due to any general distortion in crystals observed in topographs of the section type.

A rigorous formulation of Babinet's Principle has been found by Copson and by Meixner for perfect conductors. A recently published theory of diffraction by holes in absorbing and transparent screens suggests a generalization of Babinet's Principle to absorbing and transparent materials. The generalized form of Babinet's Principle is not a rigorous statement; it holds only for certain approximate solutions. In this paper it is used to calculate backscattering by circular disks of various reflection coefficients from zero to unity. Experimental results by Severin and v.Baeckmann support this theory. It is expected that, in a succeeding paper, it can be shown that scattering by solid bodies may be calculated in a similar way if the bodies are bounded by plane surfaces large compared to wavelength.

This paper quantitatively describes the optical distortion in neodymium‐doped glass which is induced by pump radiation. We have found the optical path length at 6328 A dependent on four primary effects: (1) change in physical length; (2) change in refractive index due to temperature rise; (3) change in index resulting from stress; (4) change in index associated with an excited‐state population of neodymium ions. Section I presents the experimental techniques used and the results obtained. Included in this section are measurements of optical‐path‐length variations, pump‐induced birefringence, change in physical length, change in refractive index, bulk temperature rise, and the deflection of a pencil of rays. Section II compares the results of Section I with the theory set forth in the previous paper. Good agreement between theory and experiment is achieved provided a term which takes account of the index change associated with an excited‐state population of neodymium ions is included. This term arises from...

The extension of Sommerfield's problem to a moving semi‐infinite lossless medium is considered in this paper. The analysis is limited to the determination of the space wave in the far zone. This is the geometrical optics solution of the problem and is carried out simply by utilizing the results of the plane‐wave reflection—refraction problem obtained in a previous paper. The study includes both the vertical and the horizontal dipoles. As expected, the motion of the medium does not significantly affect the radiation pattern unless the velocity is comparable with that of light.

The feasibility of a beam‐addressable memory using EuO as a storage medium and GaAs laser as a transducer has been discussed in a previous paper. In this paper we shall present the results of a series of high‐speed, dynamic read/write experiments and discuss the system implications of these experiments. A mechanical scanner was constructed to carry out the dynamic read/write experiment and a refrigeration system was used to provide both the cooling of the GaAs laser and the storage medium. Writing was accomplished by pulsing the laser as the light spot scanned across the film surface. The energy density required to write a 5 μ spot is below 10−2 erg. This is within the capability of GaAs lasers, hence writing time in tens of nanoseconds was easily achieved. Reading is achieved by scanning a cw GaAs laser beam across the film surface and detecting the magneto‐optic signal through a cross polarizer by a PMT. Due to the large magneto‐optic effect, very high‐speed readout is achieved. The high‐speed read/writ...

The most popular model for a field emission diode has been a spherical cathode inside a concentric spherical anode. A much more accurate model assumes the cathode is an equipotential of a sphere centered on the tip of a narrow cone. The authors have discussed this latter model in some detail. The purpose of this paper is to point out similarities between the sphere and the sphere‐on‐cone models and to correct errors in our previous paper. The similarities discussed here make earlier results more useful in concept and practice. In particular, the sphere‐on‐cone model predicts a source size from 1.5 to 2.6 times larger than predicted by the simple sphere model that is normally used.

An error in the previous paper of the same title, concerning the discharge with bulk generated carriers, has been corrected. The conclusions of the previous paper are still qualitatively correct.

This paper is specifically aimed at the types of problems and their solutions for large, high‐field magnets which require high‐current‐density operation for reasons of size and economy. It is apparent that magnet stability can be varied to some extent to suit the specific use to which the magnet is put without sacrificing vital packing factors. The treatment in this paper will include some aspects of the methods used and illustrations from tests on magnets with Nb3Sn ribbon lengths ranging from 0.7 to over 90 km. A magnet wound with over 90 km of ribbon for the Lewis Research Center consists of 22 modules arranged in five concentric rows, the placement of the modules determined by requirements of axial strength, cooling, and placement of versions of Nb3Sn ribbon. The magnet was connected such as to permit powering of up to four groups of modules with separate supplies. The highest field attained is 135 kG in the center of the 6‐in. bore (140 kG at the inner windings); this using three power supplies. The electrical system is designed to provide combination of voltage and current ramping for each of the four powered sections. Upon going normal, the power supplies are disconnected and the magnet sections are shorted to permit circulating currents with slow field decay. The required degree of stabilization is achieved by a combination of silver‐plating on the ribbon, insulated sheets of copper interleaving between each layer, copper strips distributed across each layer and shorted to the turns, and large cross‐section copper turns which act as secondaries. This combination of stabilizing means had been determined chiefly by empirical methods. Of interest is the dynamic response of each of the voltages of the 22 modules of the 6‐in.‐bore magnet upon normalcy. Visicorder traces show a complex pattern of resistive and induced voltages from which a sequential spatial and temporal pattern of normalcy propagation can be derived. The initial voltage appeared on the inner (higher field) row of modules in a location approximately two thirds of the distance out from the magnet central plane, generally fanning out to include the remaining modules within the subsequent two seconds. Because of the special provisions taken for stabilizing, the total field decay occurs over the order of 10 sec and the induced voltages are no more than 3 V for any one module. Results are presented for 3¼‐in. bore, 750 m test coils wound with axial shorting strips with a range of resistivities from 1×10−8 Ω·cm (copper) to 1×10−5 Ω·cm (phosphor bronze) to illustrate the relative degree of independence of critical current on coil‐charging rate achieved with the shorting strips of higher resistivity. This is explained by a computer analysis which relates the local inductance of a coil section with the power expended in the shorting strips such that at least a qualatative balance can be made between these effects and the desireable voltage protection achieved with shorting strips of lower resistivity. Preliminary test results are given for 50‐cm i.d. magnets wound with 50 km of ribbon which were tested in the superfluid region (1.92°K). Consistent with previously published results on smaller magnets, the critical current improved by approximately 30% over that at 4.2°. It becomes obvious that the methods of stabilization described, when referred to an optimum which is consistent with the magnet usage, will yield a high current density in the windings and permit very large bore, high‐field magnets to be built.

In this paper some new observations on electrically induced damage in NaCl single crystals are presented. Microscopic studies made on surfaces normal and parallel to the applied electric field and inside the sample allowed us to determine the crystallographic and geometric characteristics of the breakdown channel, the nature of the different damaged zones around it, and their manifestations on the external surfaces of the sample. A mechanism based on the model of Bullough and Gilman is proposed to explain the experimental results. It is suggested that as a high amount of energy is transferred to the solid in a very short time compared with the elastic relaxation time, an interior implosion can be generated. An implosion of this kind would originate high‐intensity shock waves, which would be responsible for the observed damage by causing intense heating, sublimation and decomposition of the material, spallation, and cleavage.

This paper reports jet time of arrival, brightness‐temperature profiles, and pressure histories over a greater distance and for longer observation times than have been previously reported. A Voitenko compressor was used to produce a high‐energy jet of oxygen through a 2‐cm‐i.d. 350‐cm‐long steel pipe containing air initially at 2.5 μ of mercury. Velocities for the various identified jet components varied from 2.46 to 7.95 cm/μsec. Brightness temperature, and pressure profiles were obtained at specific locations along the pipe. A maximum brightness temperature of 136000°K was measured for the plasma jet as it started down the exit pipe. The results suggest that delayed entrainment of ablated wall material was the predominant factor in reducing pressure and temperature in the slower components of the jet.

This paper discusses two characteristics necessary for efficient laser‐induced transfer of organic colorants. Results analyzed on a scanning electron microscope and scanning microdensitometer suggest that the material transfer is caused by melting and vaporization.

It has been shown that effective uniaxial anisotropy fields Hk″ of epitaxial magnetic‐garnet bubble materials can be found from an optical measurement of the sample's easy‐axis susceptibility. The susceptibility is influenced by the cubic anisotropy which the materials possess in addition to their induced uniaxial anisotropy. This paper examines in detail how the optical measurements are affected by various ratios of cubic and uniaxial anisotropies. In particular, it is found that Hk″ can be found accurately using this technique for a wide range of material parameters which includes bubble materials. A procedure which corrects for sample misalignment is presented along with a method by which the cubic and uniaxial anisotropy constants for a material can be calculated from measurements of its Hk″ and magnetization.

A numerical solution of the nonlinear macroscopic laser‐fluid equations for propagation of a Gaussian laser pulse in air is described. The concept of ``utility analysis'' of numerical differencing schemes is introduced. With the computation scheme used, the laser pulse could be followed for only 10−5 sec; so enormous energy was put into the pulse to enhance the interaction with the fluid. Thus the initial pulse distortion could be observed. Analytical evaluation of the computer results produces a detailed quantitative check and suggests that a combination of analytic and numerical methods would allow a pulse to be conveniently followed for much longer periods of time. The preceding paper by the same authors describes various types of instabilities to be anticipated for propagation over long periods of time or with large powers.

Antenna voltage breakdown arising from the transmission of high‐power microwave radiation may be suppressed on a reentry vehicle by injecting electrophilic chemicals into the flow field. This paper describes numerical procedures for calculating the amount of high‐power microwave radiation that can be transmitted through a plasma chemically seeded with an electron‐attaching substance. The power incident on a reentry plasma slab may be sufficient to induce electron temperature changes, resulting in variations in time of the electron density and effective collision frequency. The plasma properties are determined as a function of time by numerically integrating the two continuity equations for the electron and positive‐ion densities. The processes of electron impact ionization, electron attachment, detachment, and recombination are taken into consideration. The diffusion of the electrons and positive ions in the ambipolar limit is influenced by the presence of negative ions. Runge‐Kutta numerical integration ...

It is convenient to measure foil weight and area and use known values of density to calculate an average thickness. It is also possible to measure the transmission of monochromatic x rays through the foil and use accepted values of the absorption coefficient to determine foil thickness. If this x‐ray transmission measurement is performed over a large area of an irregular foil, the resulting calculation of average foil thickness will not be in agreement with the weight‐area method. The purpose of this paper is to indicate the error introduced in the average thickness measurement by examining the disparity in transmission between a uniform foil and several nonuniform foils having the same average thickness.

This paper is composed of five sections. Section III analyzes the Butler‐type and flat‐plate lenses of the accelerating lens system in the scanning electron microscope (SEM) using a field‐emission gun. Section IV presents the result of an analysis of some new accelerating lens systems when three anodes are present. The lens systems described in sec. IV are designed particularly for the low‐energy SEM. Their major advantage is that the accelerating voltages can freely be changed in a wide range (from 300 V to about 100 kV) by merely adjusting the control voltages between the tip and the second anode without changing the focal point, etc. The resolution of the system and the beam current on the specimen seem to have the possibility of reaching 1000 A and 10−8 A respectively, at accelerating voltages higher than 3 kV. Therefore, these lens systems also seem appropriate for the scanning Auger electron microscope.

Many laser drilling applications require that the shape of the drilled hole be carefully controlled. In order to successfully do this it is necessary to understand the laser drilling process. This paper reports on a quantitative model which predicts the depth and shape of a hole drilled in alumina ceramic by a ruby laser. Both experimental and theoretical results indicate that the predominant drilling mechanism for this application is not one of surface absorption and conduction inward, but one in which laser energy is absorbed throughout the bulk of the ceramic. The depth and shape of holes drilled in ceramic have been accurately predicted from the measured beam energy density distribution. Finally, it is shown that the radiation pressure of the focused beam plays an important role in the romoval of molten material from the heated region.

This paper describes electro‐optically induced tunable deflection in the plane of a waveguide structure by utilizing the liquid‐crystal property of tunable birefringence together with appropriately designed electrodes. The magnitude of tunable deflection achieved in this experiment (>20°) had only been demonstrated in passive structures in the past. Furthermore, by changing the device parameters slightly, electrically controlled total internal reflection or refraction in the plane of the waveguide structure was demonstrated. This allowed operation of the device as a switch where the guided beam was deflected or ``switched'' through a very large angle (>70°) in the plane of the guide.

In this paper we report on the observation of acoustoelectric effect (transversal and longitudinal) in the layered structure LiNbO3–Si by means of capacity probes, situated on one side of LiNbO3 thin plate with surface acoustic waves propagating along the opposite side adjacent to the Si plate. These effects arise due to the penetration into the silicon plate of the electric fields of the surface acoustic wave propagating along the LiNbO3 plate. The transversal effect was revealed to be even (i.e., did not change its sign with a reversal of the direction of surface acoustic wave propagation). The longitudinal effect was revealed to be odd. In high‐conductivity Si samples (σ≥10−4 Ω−1 cm−1) the transversal effect predominated, in low‐conductivity samples the longitudinal effect predominated. Experimental results on the investigation of the transversal acoustoelectric effect as a function of acoustic intensity, conductivity of the silicon specimen, and dc‐drift electric field are given. The comparison of these results with the theory of acoustoelectric effect in layered structures is carried out.

In this paper we show that photostimulated exoelectron emission resulting from the plastic deformation of a metal originates solely from the slip lines produced on the surface. Conclusive evidence is provided by micrographs formed by direct electron optical imaging of the exoelectrons. The exoelectrons are emitted only from bare metal revealed by a localized rupturing of the natural surface oxide during the formation of the slip step. This contrast mechanism is unique and offers a new form of electron microscopy for the study of plastic deformation of metals.

The paper presents a study of various aspects of propagation in the TM01 mode along a dielectric‐rod waveguide immersed in plasma. Expressions are derived and characteristics obtained for the dispersion relation, phase and group velocities, as well as power flow in and around the guide in the loss‐free case of propagation. The dispersion relation reveals that the TM01 mode is the dominant one with backward wave characteristics for low negative values of ep/ed, where ep and ed are the dielectric constants of the plasma and the rod, respectively. The phase velocity is found to be always greater than the velocity of a plane wave in the rod medium if ep is positive, while for its negative values the phase velocity can be either greater or less. From the point of view of power concentration, the structure acts as a very good surface waveguide, particularly for high negative values of ep/ed. The attenuation coefficient is subsequently derived by the standard perturbation method, assuming that both the plasma an...

Although it is known that the small‐signal gain calculations are in agreement with experimental results of lowest threshold for the zero‐order mode in the thick‐cavity PpnN junction laser, the theory for lasing mode stability under large‐signal conditions has not been previously investigated. In this paper, a study is given of the geometrical conditions under which the best dynamic stability is obtained for the lasing mode in a structure capable of supporting several modes. Solutions are obtained for the carrier and gain spatial profiles in the active region of an injection laser under large‐signal conditions by accounting for both spontaneous and stimulated recombination. The effect of stimulated emission in a lasing mode on the gain of a nonlasing mode is calculated. It is found that, for certain positions of the p‐n junction within the optical cavity, an increase in lasing power in the zero‐order mode suppresses the gain in higher‐order modes. The optimum geometry for dynamic stability of the lasing zero‐order mode is obtained when the gain region is two‐thirds of the waveguide thickness, consistent with the condition for lowest zero‐order mode threshold. In addition, the results also show that the quasi‐Fermi level in the gain region changes as a function of stimulated power in such a way as to keep its spatially ``averaged'' value nearly constant. However, the position of the quasi‐Fermi level at the p‐n interface increases with increased optical power, thereby leading to a finite and positive junction differential resistance. Finally, for a double‐heterostructure (DH) laser the calculated internal conversion efficiency, which is the ability of the stimulated field to extract power from the junction, is shown to decrease significantly when the thickness of the active region exceeds a carrier diffusion length.

The generalized Maxwell Garnett theory developed in the preceding paper is utilized here to specify the state of roughness of a surface. Both thick and thin metal samples are measured on the ellipsometer. In the interpretation, the surface roughness layer is replaced by a smooth but anisotropic medium whose optical behavior is assumed to be governed by the generalized Maxwell Garnett theory which specifies a roughness layer by two parameters d and q. Success of the interpretation is judged according to the degree of independence existing between the two parameters d and q and the angle of incidence. Experimental results on several metals indicate that in many cases the surface roughness and not an oxide layer is responsible for the variation of ellipsometer parameters ψ and Δ from that of a truly smooth bulk material surface.

This paper reports results obtained through computer simulation of the thermally activated glide of an idealized dislocation through a random array of point obstacles. The array size is fixed at 999, and the dislocation‐obstacle interaction is taken to have a simple step form. The variables governing glide are then the resolved shear stress, the temperature, and the obstacle strength, which may be phrased as dimensionless parameters. The principal subjects studied are (1) the stress required for athermal glide at a given obstacle strength and the characteristics of the obstacle configurations which determine this stress, (2) the glide path taken by the configuration and the characteristics of the obstacle configurations encountered along this glide path, (3) the velocity of glide and its dependence on the stress, the temperature, and the obstacle strength.

Micromagnetics predicts that domain nucleation in an in‐plane field in mechanically rigid uniaxial films with easy axis normal to the faces should take the form of stripes parallel to the field. This prediction does not agree with observation in some real films. It has been shown previously that the magnetoelastic interaction in deformable films may cause the stripes to be perpendicular to the field when the films are thick enough. Quantitative assessment of this effect is difficult because the magnitudes of the magnetoelastic constants are not accurately known, and because high‐quality epitaxial films are at least partly constrained from deforming. In this paper we discuss another interaction which can cause the stripes to be perpendicular to the field in a [111]‐oriented cubic film, such as bubble‐device garnet. The interaction energy is a dipolar energy brought into play by the effectively trigonal anisotropy. It vanishes when H is along [112] and is maximum when H is along [110]. Quantitative evalua...

Microwave components incorporating ferrite elements are primarily waveguide devices. Success with these devices has yielded a wide range of useful commercial products. However an underdeveloped area for microwave ferrite application is microwave optics. Due to the complexity of design and observed anomalous behavior, ferrites have not found popularity as refraction elements. The present paper presents an initial assault into the analysis of refracting ferrite prisms and lenses. The anisotropic indices of refraction and angles of deviation were calculated for an isosceles ferrite prism magnetized in three orthogonal directions and the focal lengths of an axially magnetized thin double‐convex ferrite lens were evaluated for various values of saturation magnetization.

This paper reports on measurements with multiple techniques delineating the complete sequence of events from the primary streamer to the arc phase in the common spark transition for relatively small negative point‐to‐plane gaps applied by pulsed potential. The observations cover a range of gaps, in room air, from 3 to 7 cm long, covering the whole range of potentials from streamer onset to in excess of 30% above the standard sparking threshold. It is shown that starting with the primary streamer, which usually fades in midgap and occasionally crosses the gap, the secondary and tertiary streamers are produced by a succession of ionizing waves of potential and due to an increase of the potential applied across the gap. If overvoltage exceeds 30%, the tertiary streamer comes close to the anode and induces return ionizing waves, which lead to the thermalization of the arc. At lower overvoltages there is a dark phase lasting for about 10 μsec. During the dark period, the resultant positive ions and electrons move separately to the cathode and to the anode. The arrival of these new electrons at the plane causes very fast luminous ionizing waves which lead to the thermalization of the arc. After the last pulse, the thermalization follows through gas heating for a time from 100 to 150 nsec.

The paper gives a description of some tests carried out in preparation for the construction and development of an apparatus for artificial atomic disintegrations. The problems involved are (i) the focusing of a beam of 10–30 kv hydrogen ions from a canal‐ray ion source (glow discharge type) and (ii) the behavior of a cascade acceleration tube of the Coolidge type. In particular it was necessary to know the efficiency of the latter, i.e., the ratio of output to input currents. The general properties of electrostatic focusing systems are first treated briefly, and adequate references are given to enable those interested in the problem to pursue the matter further. It is pointed out that in view of the aberrations present, the constants of our lenses cannot be accurately calculated and we have therefore concentrated our attention on presenting the results in a concise form. Several lens systems were used to focus the canal‐ray beams and details are given in tables. It was found possible to focus at least 50 ...

This paper describes an experimental model of a combination Kerr cell camera and flash illumination unit designed specifically for the photography of projectiles under conditions of strong ambient illumination. Specific cases wherein such conditions are found are considered and the applicability of the Kerr cell as a secondary protecting shutter is described. A description is given of a pulse forming network—pulse transformer circuit designed to apply an operating voltage pulse to a Kerr cell of thirty‐six (36) kilovolts amplitude and one point nine (1.9) microseconds duration. Limitations inherent in the present equipment are considered together with proposals for overcoming these defects in future models. Typical results are presented, including (a) a picture taken with the unit showing a twenty‐millimeter shot at the time of emergence from the muzzle of a gun, and (b) a picture of a thirty‐seven millimeter shot taken shortly after penetration of a metal target plate.

The investigation contained in this paper gives a general treatment of the theory of biconical antennas based upon Smith's formulation of the problem. For the case of small‐angle cones, an expression of the effective load admittance is obtained which is the same one that Schelkunoff derived based upon two rather ingenious methods, both of which, however, are not as rigorous as the present one. As an illustration of another application of the analysis, a treatment is given of the characteristics of biconical antennas where the space between the cones is filled with a dielectric other than air.

Schwarz and Hora have observed emission of radiation from an electron beam that was modulated by laser light in passing through a thin film. The modulated beam radiated at the modulation frequency on entering a dielectric (nonfluorescent) target material. In this paper the mechanism of emission of radiation of a modulated electron beam is studied on the simplified model of a klystron cavity. It is found that one modulated electron alone is incapable of emitting a photon coherently at the modulation frequency. However, the expectation value of the field intensity does show the expected resonance behavior. If the wave functions of n electrons per unit length overlap they contribute coherently to the expectation value of the field intensity. It is thus the collective interaction of many electrons with overlapping wave functions that makes possible the coherent emission of light at the modulation frequency.

The structure of static walls is analyzed assuming that the film thickness is much larger than the wall width. It is shown that several different types of wall structure can exist. For the normal wall type the twist angle (angle between the wall magnetization at the midplane of the film and at the film surface) is approximately π/2. For the first anomalous type this angle is approximately −3π/2, for the second type approximately 5π/2, etc. The width and energy of such walls are calculated using (i) a Bloch‐line approximation and (ii) a sinusoidal variational trial function (as in Paper I of this series). The ratio of the energy of a twisted wall (E) to the energy of an untwisted wall (E0) can in all cases be represented as E/E0=(1−βσ)1/2, where σ=4πM0/Ha [M0 is the saturation magnetization, Ha is the anisotropy field]. According to the first method β=0.692 for the normal wall type and β=0.692− (π/c)(D/2πM)1/2 for the first anomalous type. Here 2c is the film thickness, D=2A/M0, and A is the exchange stiff...

In this paper we present a theory to explain the observed lens effect produced by a photocurrent in Cds. An applied dc voltage causes local heating due to the presence of a localized photocurrent produced by a focused laser beam. The local heating causes an increase in the index of refraction and hence focusing. The theory predicts that the magnification should be linear in the power dissipated by the photocurrent and these predictions fall very near the measured values of magnification for different values of photoconductance, with no fitted parameters. In order to explain the threshold effect observed in some Cds samples the change in the index of refraction with temperature of Cds is measured over a temperature range of 20°–350° and is found to be dN/dT=1.5×10−4 (°C)−1.

This paper is concerned with thin‐film optical waveguides using anisotropic and gyrotropic materials, which may play an important role in the field of integrated optics. As a fundamental problem on such waveguides, normal (propagating) modes are analyzed here by the Rayleigh‐Ritz variational technique. The analysis can be interpreted directly in terms of coupling of normal modes of the basic guide with simpler material parameters. Results are placed in the form of a matrix eigenvalue problem suitable for computer calculation, whose eigenvalues and eigenvectors lead to propagation constants and field expansion coefficients, respectively. Characteristics of anisotropic guides are discussed and compared with those of conventional isotropic guides. As a typical application TE↔TM mode converters are analyzed in some detail and numerical examples are presented.

The paper is concerned primarily with the electron guns employed in electron microscopy.The position of the image of the cathode, the magnification, and the divergence of the beam leaving the anode are calculated for a three‐electrode electron gun with plane electrodes and circular apertures both for zero and battery bias. The simplifying assumption is made that the electrostatic lenses are thin. The results are compared with the experiments of Johannson. The extension of the results to the gun used in the transmission electron microscope is considered with the aid of electrolytic trough measurements. The case of a gun biased by a cathode resistor is also discussed.

This paper describes an investigation of the origin of moire patterns which occur in display‐type lowenergy electron diffraction apparatus. With both planar and spherical geometry, ``real'' multiple source moire patterns have been observed. With planar geometry, quantitative comparison of experiment and theory for the average moire fringe spacing and pattern location are shown to be in good agreement. Spherical geometry patterns can be understood qualitatively on the same basis.

This paper describes a structure, namely, a cross‐wound twin helix which overcomes the disadvantages of a conventional helix for high‐voltage traveling‐wave tubes. The disadvantages of a single helix suitable for high voltages are: (1) the impedance for electron interaction is reduced because of the energy content of the noninteracting space harmonics, and (2) the high impedance of some of the space harmonics can result in backward‐wave oscillation. In a structure consisting of two helices wound in opposite directions, the symmetry of the fields results in most of the electric energy being stored in the fundamental component and most of the magnetic energy in the space harmonics. This results in a higher impedance for the fundamental component and a reduced impedance for the space harmonics. Typical numbers for dimensions suitable for 10‐kv operation are an increase of a factor of 2 in the fundamental impedance and a reduction of a factor of about 20 in the −1 space harmonic for the twin helix as compared to the single helix.

While wave propagation in gyromagnetic media has been investigated extensively in the technical literature, little attention has been given to the excitation of such waves by a prescribed source. This problem is treated in the present paper. To render the analysis tractable, the source function is taken as a time‐harmonic line source of electric currents with a rapidly varying phase, embedded in an infinite homogeneous gyromagnetic medium whose axis of magnetization is perpendicular to the source direction. For further simplification, the operating frequency is taken to be near gyromagnetic resonance. The resulting model incorporates relevant anomalies of the radiation process, and also serves as a prototype for more practical thin slab configurations. The analysis is performed for permeability tensors in which spin exchange effects are ignored and included. In the former case, the refractive index surface may have open branches and gives rise to an infinity in the total radiated power (infinity catastrophe); this anomaly is removed when spin exchange is accounted for. Detailed study of the radiation fields and radiated power densities shows that except for certain initial directions, the outward power flow is almost entirely in the electromagnetic waves, and the total radiated power in the electromagnetic waves far exceeds that in the spin exchange waves, even when the source dimensions tend to zero. These results imply that a localized electromagnetic current source does not strongly excite the spin exchange waves.