摘要:

The state of operation of a thermocouple of which (a) the bars have an arbitrary shape; (b) the properties of the materials are arbitrary functions of temperature; and (c) the composition is, under certain restrictions, inhomogeneous and anisotropic depends on three independent parameters: the currentIand the temperaturesT1,T2of the junctions. IfT2is kept constant, operating characteristics, such as curves of constant output power or efficiency, can be plotted in anI, (T2−T1) diagram. The existence of regions of generation of electricity and of cooling is proved. These regions are investigated. Possible generalization and reduction of the diagram are discussed. As an illustrative example, the cooling region of a general couple with temperature independent properties is dealt with.

ISSN:0021-8979    

DOI:10.1063/1.1735791

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

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

ISSN:0021-8979    

DOI:10.1063/1.1735792

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The kinetic and electromagnetic components of ac power and stored energy are evaluated for space‐charge waves along thin drifting beams of simple geometry. It is found that: (a) when a modulated beam is decelerated, it radiates power into the surrounding space; (b) when both fast and slow waves are excited by a common source, the real kinetic power varies periodically with distance, exchanging energy with the electromagnetic field; and (c) when a finite‐area beam is current modulated with zero ac velocity, the total power need not be zero.The energy transport velocity of a space‐charge wave is shown to equal its group velocity, when the time‐average stored energy is properly evaluated. A small portion of the stored kinetic energy propagates, together with the field energy, as an electromechanical wave along the beam. The larger part of the kinetic energy, which can be positive or negative, is transported by the motion of the beam itself.

ISSN:0021-8979    

DOI:10.1063/1.1735793

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

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

ISSN:0021-8979    

DOI:10.1063/1.1735794

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Charge multiplication as a function of reverse bias has been studied in a number of uniform siliconp‐njunctions (junctions free from defects which promote local avalanche breakdown sites). From the multiplication characteristics new data have been derived for the field dependence of the ionization rate (&agr;) for electrons. As previously found in junctions containing dislocations, &agr; obeys the empirical relation &agr;=&agr;∞exp (−b/E), where &agr;∞andbare constants andEis the field. Thus, this law is not simply a consequence of distortions to the junction introduced by dislocations or other microplasma‐inducing defects.The ionization rates and breakdown voltages for the uniform junctions can be made consistent with older data (for nonuniform junctions) if the junction fields, as determined from capacitance measurements, in the new junctions are multiplied by 0.65. The most obvious interpretation of this experimental fact is that breakdown is made relatively easier at defects because the field is actually higher by a factor of 1.55. Possible causes of such an enhancement are discussed together with alternative hypotheses for the different ionization rates.

ISSN:0021-8979    

DOI:10.1063/1.1735795

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The role of the twin planes in the rapid dendritic propagation of germanium crystals is examined on the basis of corner nucleation. A model is proposed, and it is shown that at least two twin planes must be present for continued easy propagation in <211> directions, in good agreement with experimental observations. The absence of the dendrite with only one twin is explained.

ISSN:0021-8979    

DOI:10.1063/1.1735796

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A method is devised for the calculation of molecular flow rates through pipes where the mean free path for intermolecular collisions is large compared to the dimensions of the pipes. Results of the calculation are given for a straight cylindrical pipe, a cylindrical elbow, the annulus between two concentric cylinders, a straight cylindrical pipe with restricted openings, and a straight cylindrical pipe with restricted openings and a plate to block the direct beam between the openings.

ISSN:0021-8979    

DOI:10.1063/1.1735797

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The use of a first Born approximation is open to question when the path length is greater than a mean free path in the scattering region. It is therefore of interest to develop a transport equation capable of predicting the spectral density for such cases. The general theory presented in this paper is applied to the case of multiple scattering by dielectric noise. It is independent of models for the dielectric fluctuations. A method of solution is developed for the case of forward scattering. The particular case of a monochromatic plane wave incident of a half space is discussed in detail. The results are applied to a numerical example in the troposphere.

ISSN:0021-8979    

DOI:10.1063/1.1735798

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Small angle scattering measurements have been made on distributions of particles prepared by mixing two silica sols of about 90A and 190A mean particle diameter in varying proportions. The scattering at small angles arises predominantly from the larger particles, whereas the smaller ones control the scattering at large angles, as predicted by theory. Attempts to determine the size distribution by the graphical method of Jellineket al.were unsuccessful, but Porod's result relating the scattering at large angles to the total surface area was verified. Bounds for the largest and smallest sizes were estimated from the experimental data by means of simple calculations based on the properties of the scattering function.

ISSN:0021-8979    

DOI:10.1063/1.1735799

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A solution for the paraxial orbits of charged particles in varying magnetic fields is given. The magnetic field is assumed to be azimuthally symmetric but is allowed to vary arbitrarily with time or axial distance. The instantaneous guiding center and radius vector of the orbit are given in terms of the initial guiding center and radius vector and two parameters which are determined from the solution of a first‐order differential equation containing the magnetic‐field variation. One exact and two approximate constants of the motion are evaluated and discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735800

出版商:AIP    

年代:1960

数据来源: AIP