Volume 25, Issue 6, 01 June 1954
Index of content:
Relativistic Dynamics of a Charged Particle in Crossed Magnetic and Electric Fields with Application to the Planar Magnetron25(1954); http://dx.doi.org/10.1063/1.1721717View Description Hide Description
Complete characterization of planar magnetron behavior is achieved for intermediate relativistic energies where radiation loss is of no serious consequence. The cut‐off condition in the neighborhood of the rest energy of the particle shows a linear dependency on the product of electrode separation and magnetic fieldLH rather than the classical (LH)2. The modified period assumes a particularly simple form (2π/ω[1/(1−γ2)3/2], γ being the ratio of electric and magnetic fields which reflects a voltage dependency of the period not encountered in the classical case.
A parametric solution for the periodic orbits is derived on the basis of a transformation related to the delineation of the velocity space and, as such, represents a new variety of transcendental curve which degenerates into the cycloid for the limiting case of γ→0.
The spatial‐time dependent mass, momenta, and energy relations take on especially straightforward forms in terms of the trajectory parametric solution.
On the Nature of the Transcendental Curves Associated with the Relativistic Trajectories of Charged Particles25(1954); http://dx.doi.org/10.1063/1.1721718View Description Hide Description
A detailed examination of the relativistic trajectories in the intermediate high‐energy range is made for charged particles in crossed magnetic and electric fields for generalized injection states with explicit solutions given in parametric form. The particle path relation is generally formulated, but explicit calculation is offered for the zero velocity injection only.
25(1954); http://dx.doi.org/10.1063/1.1721719View Description Hide Description
Low sputtering rates are measured by means of the probe technique in a plasma. The displacement of the probe curve along the voltage axis (and its change in shape) when the probe is covered with a material of different work function,sputtered from a sputteringelectrode, is a dependable measure for the thickness of the sputtered layer. The method is very sensitive, generally applicable, and was applied especially to answer the question of a threshold voltage U 0 for sputtering. The sputtering rate for Pt in Xe, in the region of low ion energies (50<Us <200 ev) is roughly proportional to (Us −U 0)2 with U 0=40 ev.
25(1954); http://dx.doi.org/10.1063/1.1721720View Description Hide Description
In a circulating‐fuel reactor, the circulation of the fuel causes a damping of power oscillations of the reactor. This is demonstrated under the assumption that there is no mechanical vibration coupled with the oscillation of reactor power, and that the shape of the hydrodynamic flow does not vary with time.
25(1954); http://dx.doi.org/10.1063/1.1721721View Description Hide Description
Using methyl methacrylate as an intermediate, an attempt was made to obtain a high‐resolution two‐step replica, by improving evaporation elements and evaporation method. It was found that, by using Zr, Si, and Fe, with Ge and Cr as evaporation elements, the resolution of two‐step replicas was superior to that obtained up to the present. It is also known that the resolution of replicas obtained by performing metallic evaporation after treatment by ion or electron bombardment for a methyl methacrylate intermediate replica is superior to that without bombardment. Two evaporation methods—the usual continuous method and an intermittent one—were compared. A new method for the production of surface replicas of microspecimens is also proposed. The high‐resolution replica obtained here is compared with others along with a brief consideration of the results obtained.
25(1954); http://dx.doi.org/10.1063/1.1721722View Description Hide Description
Experiments are described which supply evidence on the manner of electrical conduction through the oxide cathode coating. In the first experiment, I–V characteristics were obtained using special diodes with embedded probes. Contrary to the Loosjes‐Vink theory, the characteristics for temperatures above 700°K are generally linear at high positive and negative potentials but curved at lower potentials. Other experiments would appear to confirm the presence of space change in the pores of the coating at temperatures above 700°K, and so support the Loosjes‐Vink theory for higher‐temperature conductivity. A modified conduction theory is put forward, and it is shown to fit in with all the known facts.
25(1954); http://dx.doi.org/10.1063/1.1721723View Description Hide Description
A new method of determining the cathodetemperature of the diode, triode, and multigrid tube, using high harmonic component of initial current which flows to the anode when an ac voltage is applied to the anode, is presented. The principle and apparatus of this method are described, and the causes of error in measurement are discussed. The advantage of this new method is that the temperature may be read directly; the time for measuring is extremely short; the error due to the leakage current is reduced; and it has a high accuracy (within ±0.05 percent) and good reproducibility. Results on diode 6AL5, 6H6, triode 6J6, and pentode 6SH7 taken by this method, and results taken by other method, are compared.
25(1954); http://dx.doi.org/10.1063/1.1721724View Description Hide Description
A theoretical investigation of the electromagnetic waves due to a dipole source above a grounded dielectric slab has been made by integral transforms. The solutions in integral form have been evaluated asymptotically for distant field. It is found that the fields consist of a space wave and a surface wave. The former, spherical in nature, predominates in the free space, while the latter, cylindrical in nature and with a finite number of modes, is guided along the dielectric. As a result of the existence of at least one pole of the integrand, this surface wave always exists. At the dielectric surface, the zero‐order spherical wave has a null value except the case of critical thickness; then it should be referred to the next‐order solution.
25(1954); http://dx.doi.org/10.1063/1.1721725View Description Hide Description
A mathematical solution is obtained of a two‐dimensional boundary‐value problem involving flow of electricity in a solid when Hall effect is present, it being assumed that only one type of carrier is involved and that there is no surface recombination. The solution is used to calculate the efficiency of a Hall‐effect ``gyrator,'' a four‐terminal circuit element which violates the reciprocity law, as function of relative electrode size, shape of boundary, and magnetic field strength. It is also shown how corrections must be applied in measurements of Hall voltage and magnetoresistance in short samples.
Some of the results have been checked experimentally with fields up to 22 000 gauss. The calculations have been carried out for much higher fields as well and should prove useful in studies of materials such as indium antimonide which have higher mobilities than germanium.
25(1954); http://dx.doi.org/10.1063/1.1721726View Description Hide Description
Improved polyvinyl alcohol‐silica replica techniques are described which allow for more accurate examination by electron microscopy of pigment derived microstructure in paint films. These methods complement the silver‐silica techniques which are preferable only for studying much finer details, such as molecular configurations and small distortions of the resinous binder. Procedures have been developed for stripping unaltered baked enamel films from tin plate. The underside of these free films can be examined with the improved replica techniques and it is possible to study differences in top and bottom structure of paint films. Applications of the refined replica techniques in the study of paint films are presented.
25(1954); http://dx.doi.org/10.1063/1.1721727View Description Hide Description
This paper discusses a method for finding an integral transformation applicable to certain time‐varying systems. Examples of transformations derived by the method, including Laplace, Mellin, and Meijer, are given. A convolution theorem for the general method is presented, and its use in general representation of time‐varying systems is illustrated.
25(1954); http://dx.doi.org/10.1063/1.1721728View Description Hide Description
The physical characteristics,thermoelectric power, resistivity,specific heatconductivity, and the temperature difference between hot and cold junctions determine the efficiency of thermocouplematerials. These data have been determined for Chromel P‐constantan, bismuth alloys, and the intermetallic compound ZnSb, containing small amounts of added metals.
The optimum characteristics of flat‐plate type solar energy collectors have been evaluated in combination with thermocouples, designed for maximum energy conversion. Using flat‐plate collectors with 2 glass panes, an efficiency of 0.63 percent was obtained with the ZnSb‐type alloys in combination with a negative Bi‐alloy. The commercially available ductile alloys Chromel P‐constantan, produced ten times lower efficiency. Calculations indicate that the efficiency may be increased to 1.05 percent by using 4 panes of low‐reflection characteristics.
With solar energy concentrating means (lenses), the efficiency was increased to 3.35 percent, using the above mentioned best alloy combination.
The maximum allowable cost of thermoelectric generators has been evaluated, by comparison with present methods of electric power generation.
Solar thermoelectric generators may find useful application in the tropics, as they do not contain moving parts and require very little attention. Further development is needed to determine their economical value.
25(1954); http://dx.doi.org/10.1063/1.1721729View Description Hide Description
Hardness measurements were made along radii of circular cross sections of an annealed thick‐walled low‐carbon steel cylinder internally loaded with an explosive charge. The degree of work‐hardening in the cylinder wall was found to decrease nonuniformly with an increase in distance from the surface in contact with the explosive. Each hardnessversus distance curve exhibited a series of plateaus along which the hardness remained constant. The plateaus appear to be related to Neumann bands which are present in the steel. The maximum number of twin directions in a single grain increases with the magnitude of the stress. The presence of the hardness plateaus and the increase in the number of twin directions with hardness and stress level point to the existence of critical stresses for twinning.
25(1954); http://dx.doi.org/10.1063/1.1721730View Description Hide Description
The impedance Em 2/2β m 2 P of the backward wave on helical structures is considered from the point of view of the design of backward‐wave oscillators. Curves of impedance versus ka (circumference to free‐space wavelength ratio) for single and bifilar helices are presented. Both the case of thin tape and that of round wire are treated. The impedance curves are calculated on the basis of an approximation to the actual distribution of rf current over the surface of the conductors; the use of this approximation is justified by comparison with an exact solution at specific values of ka. A proof is presented which demonstrates that the backward‐wave impedances of two tape helices are identical if the gap width of one is equal to the tape width of the other. Expressions are derived for effects of dielectric supports upon the velocity and impedance of the backward wave.
25(1954); http://dx.doi.org/10.1063/1.1721731View Description Hide Description
Loss measurements were made on ten dielectric coated wires used as surface wave transmission lines at a frequency of 9365 mc/sec. The purpose of these measurements was (1) to develop a satisfactory method for making the loss measurements, and (2) to compare the measured loss with the calculated or predicted value obtained from theoretical analysis made by Goubau. A resonance method, in which the Q of a resonator formed by short circuiting both ends of a length of line is determined, was found to be most desirable. The loss in the resonator end plates was taken into account in determining the wire loss.
A description of the apparatus required and the experimental procedures used is given. A brief discussion of alternative methods for making the loss measurements, some of which have been tried, is also given.
The losses of the wires measured ranged from about 3.0 db/100 feet for thin dielectric coatings to about 11.5 db/100 feet for thick dielectric coatings. The agreement between measured and calculated losses of wires for which the constants of the dielectric coating are known is considered good.
25(1954); http://dx.doi.org/10.1063/1.1721732View Description Hide Description
Thin films of antimony were condensed onto substrates at various temperatures. Films deposited at liquid oxygen temperatures showed large negative temperature coefficients of resistance. In general, reversible resistance changes occurred if the films were cooled below a temperature previously reached; irreversible changes took place if the films were heated above that at which they were prepared. Activation energies were calculated from logR vs 1/T curves and gave values of ∼0.07 ev for low temperatures and ∼0.13 ev for high temperatures. There appeared to be little or no influence of evaporation rate or thickness on the activation energies. A theory based on lattice defects is proposed in order to explain the electrical behavior of the films.
25(1954); http://dx.doi.org/10.1063/1.1721733View Description Hide Description
The Wiener‐Khintchine theorem which connects the autocorrelation function and the power spectrum of a stationary time series by means of a Fourier cosine transform is well known. It is the purpose of this paper to generalize the theorem to deal with nonstationary time series.
- LETTERS TO THE EDITOR
Comments on the Paper of Alan G. Mencher, ``Epicentral Displacement Due to Elastic Waves in an Infinite Slab''25(1954); http://dx.doi.org/10.1063/1.1721734View Description Hide Description
25(1954); http://dx.doi.org/10.1063/1.1721735View Description Hide Description
25(1954); http://dx.doi.org/10.1063/1.1721736View Description Hide Description