摘要:

The equilibrium temperature distribution in an ideal metal rod, one end of which is subjected to an intense electric field, is studied. Particular attention is focused on the case where the emitting end cools down, and the necessary conditions for this effect are derived. Viewed as a ``heat pump,'' the maximum rate of heat flow as a function of emitter temperature is derived, and it is found that rates in excess of 0.1 cal/sec/cm2are possible at room temperature if the emitter work function is less than an electron volt.

ISSN:0021-8979    

DOI:10.1063/1.1702470

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The Holstein‐Biberman theory of the transport of resonance radiation in gases is generalized to include the case in which the boundary is partially reflecting. The problem is formulated in a manner which follows conventional transport theory somewhat more closely than the earlier treatments of Holstein and Biberman. Using the incoherent scattering approximation, we first write down the two coupled Boltzmann equations describing the mutual transport of excited atoms and resonance photons. The photon equation is then solved, with (diffuse) reflecting boundary conditions, by a slight extension of the interreflection method, and inserting the result into the excited atom equation leads at once to the appropriate generalization of the Holstein‐Biberman transport equation. The kernel of this integrodifferential equation,G(r,r′), represents the mean probability that a resonance quantum emitted atr′is absorbed atr, taking into account the contribution of paths which strike the boundary an arbitrary number of times;G(r,r′) is expressed quite generally in terms of the resolvent kernel of the interreflection equation. The theory is used to calculate the effect of a slightly reflecting boundary on the imprisonment time in a gas discharge.

ISSN:0021-8979    

DOI:10.1063/1.1702471

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A simple modification of Angstrom's classical method for the determination of the thermal diffusivity of thermoelectric materials is described. Using the Peltier heat generated at the junction of the specimen and a current lead as a periodic heat source, symmetrical temperature variations may be established in the specimen and the diffusivity derived from the propagation constants of the variations. Results of measurements at room temperature on lead telluride are presented.

ISSN:0021-8979    

DOI:10.1063/1.1702472

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

In order to compare point defect formation in germanium through different modes of production, Hall measurements have been made on germanium after different treatments. The same starting material was used in all experiments, namely, 5 ohm‐cmp‐type germanium. Markedly different behavior was observed. For the electron bombarded material, the number of carriers is reduced at all temperatures below room temperature, while the quenched material shows an increase at all temperatures. The deformed material exhibits intermediate behavior, with the carrier concentration increased at high temperatures and decreased at low temperatures. This is accounted for by an energy level scheme similar to that of James and Lark‐Horovitz.

ISSN:0021-8979    

DOI:10.1063/1.1702473

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An analysis is presented of the role which stable electron oscillations of large amplitude may play in determining observed ``steady‐state'' characteristics of a plasma‐filled thermionic diode. The mechanism considered is that of coupling between electrostatic plasma oscillations, driven by the energy of the entrant electron ``beam'' from the emitter surface, and the potential distribution in the emitter sheath region. In operation such that net current flow is controlled by the sheath potential distribution, it is found that the time‐averaged net current may increase markedly in transition from nonoscillatory to oscillatory operation, with a concurrent change in cell and load potential drops such that the diode acts as a negative resistance source of potential over a limited range. Conditions which restrict attainment of the oscillatory mode are discussed, and it is found that large amplitude electron waves may be generated and maintained over a fairly wide, and experimentally accessible range of plasma electron density. Comparison is made with some experimental results, and an experiment is suggested for direct test of the driven‐wave hypothesis discussed herein.

ISSN:0021-8979    

DOI:10.1063/1.1702474

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The electrification of the dust of KCl monocrystals irradiated with &bgr; rays is influenced by 3 factors: absorption of electrons in the crystal, creation ofFcenters, and secondary emission. TheF‐center concentration in crystals irradiated with &bgr; rays for various irradiation times was measured spectrophotometrically. Based on theF‐center model and with the help of statistical calculations the relationship between theF‐center concentration in the crystal and the surface charge due toFcenters was found.

ISSN:0021-8979    

DOI:10.1063/1.1702475

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The consequence of the principle of microscopic reversibility used for deriving the reciprocal relations in the linear phenomenological coefficients is derived from the classical hypothesis of the separability of individual processes. The application of the separability principle to nonlinear systems is illustrated with an example, and its ability to suggest microscopic mechanisms is demonstrated. The nature of independence among the processes is discussed in more detail than has been done before, and the number of unknowns, conditions, and the minimum number of experimental coefficients are calculated in the process of finding the independent fluxes and forces. The inapplicability of the principle of minimum entropy production to nonlinear systems is confirmed, and a new dissipation function is found which is a minimum with respect to variations in all the unprescribed forces in a steady state. Such a function is found to be the integral of part of the change of the rate of entropy production with respect to the forces as discussed by Prigogine. The integrability of such a change is due to the classical principle of separability. Since this function can only decrease with time in all natural processes, it is given the name of thermokinetic potential. A possible separation between phonon drag and the energy of transport, and also that between the charge of transfer and the electron wind effect, by measuring higher‐order phenomenological coefficients is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702476

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The development of a reagent for dislocation etching of high‐purity zinc alloys with copper or aluminum, not requiring decoration of the dislocations, allowed the study of dislocation arrangements in bent alloy crystals. Most of the dislocations were found in the unannealed condition to be arranged in disconnected wall segments perpendicular to the basal plane, showing that the solutes had little, if any, effect on mechanical polygonization during bending. Their effect on the rate of subsequent thermal polygonization and of subgrain growth was also found to be surprisingly slight.

ISSN:0021-8979    

DOI:10.1063/1.1702477

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An approximate analytical approach for determining the temperature distribution in a hollow cylindrical cup of radiusC, having a base thicknessH, with a stem of radiusA, and lengthL, is given. The outer radial surface of the cup is held at a temperatureT0and the temperature at the bottom of the stem isTs. All other surfaces are adiabatic. This geometrical arrangement is used to observe marker motion under the influence of a large thermal gradient in a thermal diffusion experiment described in the following paper. In this setup, only the sink temperatureTsand the temperature at the bottom of the cupTmcan be measured. Equations are presented which enable one to calculate the temperature and its gradient along the axis of this arrangement with relative ease for the physically important caseA/C<¼. In the region along the axis above the cup‐stem interface, the temperature at any point is given in terms ofTm, Ts, and functions which depend only upon the ratioA/H. A table of these functions is presented for the cases &pgr;A/H=0.4, 0.8, and 1.2.

ISSN:0021-8979    

DOI:10.1063/1.1702478

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Measurements have been made of relative marker movements in Au and Cu in the presence of temperature gradients of the order of 1200°K/cm. These experiments yielded results which indicate that a net vacancy current is established in these metals under appropriate experimental conditions. The magnitude and direction of the observed effects are consistent with kinetic theory predictions in conjunction with previously determined vacancy energies. A three‐dimensional extension of existing kinetic theory is developed and important factors which do not appear in one‐dimensional treatments are discussed. Porosity development in Cu was found under certain conditions and this may be a visual demonstration of the existence of a thermal diffusion effect in Cu.

ISSN:0021-8979    

DOI:10.1063/1.1702479

出版商:AIP    

年代:1962

数据来源: AIP