Theoretische Modelle des katodischen Brennflecks von Bogenentladungen

Presuppositions, theoretical basis, results and general experiences of numerical model calculations of quasi-stationary cathodic spots in (vacuum) arcs are summarized. The results (mainly related to copper cathodes) comprise the essential physical quantities of the cathode spot surface and (partially) of the cathode spot plasma, i.e. possible states of existence within the space of parameters. Especially, the dependence of these results on changes of the parameters and equations is investigated. Several examples are presented and interpreted. In any case, the surface roughness of the cathode is taken into account. Finally, the limitations of the model are discussed, and the great importance of non-stationary (e.g. explosive) processes within the arc spot is emphasized, though such processes are beyond the scope of this model. The paper is published in two parts. This second part comprises the application of the model equations to the numerical calculation of arc spot parameters, the discussion of the results and some aspects of further developments in the theory of cathode arc spots.     

Streuung elektromagnetischer Oberflächen- und Volumenwellen an rauhen Oberflächen. Teil I. Allgemeine Grundlagen

Scattering of Electromagnetic Surface and Bulk Waves from Rough Surfaces. Part I. General Theory A classical theory of scattering of electromagnetic surface and bulk waves on rough surfaces (dielectrics or conductors) is given. The primary wave creates a surface polarization on the rough boundary presenting the source for the radiation of scattering. These roughness-caused polarization must be considered in the wave equations and in the boundary conditions of the fields, too. General expressions for the spectral power density of surface and bulk scattering waves will be given. The excitation of surface polarization can result from primary waves homogenously or inhomogenously.     

Über die Thermische Aktivationsenergie und das Problem des Mechanismus der Emission bei der Exoelektronenemission von NaCl,Teil I

Zusammenfassung Es wurde der Wert der thermischen Aktivationsenergie und der Wert des Frequenzfaktors bei der im Zusammenhang mit dem thermischen Entfärben von F Zentren in NaCl erscheinenden Exoelektronenemission gemessen. Auf Grund dieser Werte wurde auf die Widersprüche in den bestehenden Ansichten über den Mechanismus der Exoelektronenemission und auf die Folgerungen von verschiedenen Interpretationen des Wesens ihrer thermischen Aktivationsenergie hingewiesen.

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Thermal activation energy and the problem of the mechanism of emission during exoelectron emission from NaCl

Various methods of measuring thermal activation energies during exoelectron emission by means of phenomenological relations were investigated and applied to NaCl in the temperature region of the decoloration of F centres. On the basis of the values found for the activation energy and the formal frequency factor, the author points out discrepancies existing in opinions on exoelectron emission. It is simultaneously shown that for building up a theory there is still not enough information from quantitative experimental material, and useful lines for future investigation are pointed out.

     

Zum Beugungswirkungsgrad von Volumenhologrammen. Teil II. Reflexionshologramme

In this paper we give an exact solution of the coupled differential equation system as developed by Kogelnik [1] for the case of symmetrical recording without neglecting the second differentials for the reflection volume hologram. This solution is applicable to dielectric, absorption and so-called mixed volume holograms. There are some remarkable distinctions between our results and those got by Kogelnik for the case of absorption and mixed holograms. It is shown, that under special assumptions and approximations or for special combinations of the material parameters we get the same relations as Kogelnik.     

Teil I: Zu einigen Grundproblemen der Nahrungsmittelbestrahlung

In den vergangenen 10 bis 15 Jahren wurden in vielen Ländern umfangreiche wisseschaftlice und technische Forschungsarbeiten auf dem Gebiet der Haltbarkeitsverlängerung von Nahrungsmitteln durch Einwirkung ionisierender Strahlung begonnen. Waren es zunächst nur wenige Industrieländer (USA, UdSSR, England, Frankreich), in denen diese Problematik mit beträchtlichem Aufwand bearbeitet wurde, so schlossen sich ihnen nach dem Vorliegen erster positiver Forschungsergebnisse und aussichtsreicher ökonomischer Abschätzungen—etwa um 1960—eine Vielzahl weiterer Industrie- und Entwicklungsländer an. Inzwischen haben die Publikationen über die verschiedensten Aspekte und Bereiche der Nahrungsmittelbestrahlung einen kaum noch zu übersehenden Umfang angenommen. Aus diesem Grunde ist es schon heute nicht mehr möglich, im Rahmen einer Zeitschrift einen vollständigen Überblick über das Gesamtgebiet zu geben.     

Über die Thermische Aktivationsenergie und das Problem des Mechanismus der Emission bei der Exoelektronenemission von NaCl. Teil III

The activation energy of thermal destruction of F-centra in NaCl was measured by means of optical absorption. The result value of 2.1 eV is in a good agreement with our results obtained by means of exoelectron emission and luminescence. The different possibilities of interpretation of origin of this energy are discussed. It was pointed out that there are now many arguments for its interpretation as the thermal dissociation energy of F-centra then for any other. This interpretation leads to a good agreement with the theoretical results of Pekar. It is pointed out the limited validity of Rose relation.     

Diffusion eines stark ionisierten thermischen Plasmas im Magnetfeld. 1. Teil: Berechnung des Dichteprofils

A thermal Cs-plasma was produced by contact ionization at the surface of a hot tungsten helix spanned in the axis of a cylindrical glass vessel. The plasma density profile n (r, z) as function of a magnetic field in z-direction was measured with a movable Langmuir-probe and compared to the calculated profiles. In the present 1st part n (r, z) is calculated from the diffusion equation. In the calculations collisions of the carriers with the neutrals as well as Coulomb collisions are taken into account. This leads to a nonlinear partial boundary value problem. Methods for numerical solution and numerical solutions are given.     

Grundlagen der Thermodynamik eines Systems mit verschiedener Bahn- und Spintemperatur. I

The orbital and spin energy of aFermi orBose gas with different orbital and spin temperature depend onboth temperatures. This new thermodynamic behaviour demands a new formulation of the foundations of thermodynamics for such systems. In the present paper the fundamental thermodynamic notions (variables of state, work, adiabatic processes) are formulated and the definition of an empirical orbital and spin temperature is given. The first law of thermodynamics, the definition of orbital and spin heat, and resulting conditions of integrability are discussed. There are four heat capacities (instead of the one for normal systems), the relations of which are stated.