Die theoretische Bestimmung des Elektronen-Atom-Bremsstrahlungskontinuums in abklingenden Mitteldrucksäulen von Neon und Argon im Vergleich zum Experiment

The temporal development of the electron-atom-bremsstrahlungscontinuum was investigated in the range from 200-1000 nm in afterglow discharges. The investigations were performed for the rare gases neon and argon and under medium pressure conditions. The temporal behaviour of the continuum results from the calculation of the time altering distribution function of electrons using the instationary Boltzmann-equation. Parallel to this computations time resolved measurements of the decaying continuum were performed for some ranges of wavelengths. Considering the difficulties in the precise knowledge of the real decay of the electric field during the afterglow a satisfactory agreement in calculated and measured time decay of the continuum was obtained.     

Chaos in einem dissipativen Strahl-Plasma-System

A system of four ordinary differential equations is derived to describe the behaviour of an unstable beam-plasma-system. Numerical studies show regular as well as chaotic long time behaviour of the wave amplitude. To characterize the chaotic attractors found in the region of maximum growth rates the Poincaré maps and the greatest Lyapunov Characteristic Exponents were calculated.     

Die Relaxation der Isotropverteilung und makroskopischer Kenngrößen der Elektronen im abklingenden feldfreien Neon-Plasma

Relaxation of Distribution Function and Macroscopic Parameters of Electrons in Temporal Decaying Neon Plasma without Field Heating We investigate the field-free collision-dominated relaxation in the afterglow of a weak ionized plasma in the first period of temporal decay which is determined especially by the quick alterations in the electron component because of the small inertia of electrons. Therefore the evolution in time of the electron distribution and hence the macroscopic coefficients determined thereby are calculated in dependence on the action of elastic and exciting collisions between electrons and neutral atoms. On the basis of these results we have found characteristic times controlling the relaxation process which depend especially on the action of the different kinds of collisions. Thus it is possible to get a good microscopic understanding of the field free collision dominated relaxation of the electron component.     

Beschleunigung von Elektronen in einem Plasmabetatron

A plasma was produced by a high frequency electric quadrupole field (v=200 Megacycles) at gas pressures of 10^?4 to 5·10^?3 mm Hg in a quarz glass torus. The torus was placed between the poles of an air-core betatron with the following properties: radius of equilibrium orbit 20 cm, maximum accelerating field strength 80 V/cm, end energy 1.5 MeV. Associated with conduction currents of some 100 A, energetic Bremsstrahlung was observed and attributed to 1,2 MeV electrons. The number of accelerated electrons was of the order of 10¹¹ per pulse. The intensity and energy of the radiation, together with the time dependence of the plasma current, were observed as function of different parameters, such as the gas pressure, high frequency amplitude, induced acceleration field strength, for different gases. The energetic radiation disappears when, because of the self-induced magnetic field, the stability condition for the betatron equilibrium is no longer fulfilled.     

Experimente an einem Plasmabetatron

Recently reported measurements on a plasma betatronM II were continued and under certain conditions bremsstrahlung produced by relativistic electrons was observed associated with conduction currents of some 100 A. But also early beam disruption occured. The time τ_gg of disruption of the stream has been measured as a function of gas pressure and acceleration field strength. Most of the electrons were lost during an early stage of the acceleration process but also beam loss was observed over a long period of the acceleration time. The expected increase of the circulating runaway current due to improved parameters was not found.     

Zum Gudden-Pohl-Effekt bei einem Zink-Kadmium-Sulfid-Phosphor

Luminescence flashes in an excited ZnCdS(Ag)-phosphor occur when electric fields are put on. At ?120° C such flashes also occur if the electric field is applied some time after excitation is removed. The intensity depends on additional fields acting while the phosphor is excited by light. The observations can be interpreted if the flashes are assumed to arise near the surface instead of the interior of the phosphor.     

Zur Anwendung der Sondendiagnostik in einem polymerisierenden Plasma

On the example of the Ne glow discharge with a benzol admixture the possibility of applicating the probe diagnostic in polymerizing plasmas is investigated. Heating the probe at 900°C stetady values for the floating potential, the probe characteristic and its second derivation are obtained. The variation with time of these quantities without heating the probe yields informations about the rate of polymerization. The effect of a benzol admixture from 1% to 20% on the energy distribution function of electrons and the plasma parameters in the tube axis is pointed out. From the second derivation of the characteristic at emissive probe conditions it is possible to deduce in addition to the space potential the influence of the benzol admixture on the ionization mechanism.     

Einzelteilchen-Niveaus in einem deformierten energieabhängigen Kernpotential

The nucleon wave functions and energy eigenvalues in a spheroidal potential well of Woods-Saxon type are calculated approximately by diagonalizing the Hamiltonian in a finite subspace of Hilbertspace. The depth of the potential well is made energy dependent to account for the nonlocality of nucleon-nucleus interaction. With the pairing theory of residual interaction taken into consideration these results are used to determine nuclear deformation, energy of single-particle excited states, and an estimate of magnetic moments of nuclei with mass number about 177. Several methods are applied to calculate the equilibrium deformation. They all yield nearly identical results. The experimentally given low-energy spectra of odd-A nuclei, however, could not be reproduced satisfactorily. Some pronounced discrepancy between calculated and measured magnetic moments as already observed byMottelson andNilsson could not be reduced, either, though in other cases there is considerable improvement to their results. When comparing the structure of the calculated single particle scheme with the observed sequence of nuclear levels one is led to the conclusion that better agreement will be found for a somewhat different deformation: the nuclear shape will be given by a spheroid necked in to some degree by the equator and thickened at the ends.     

Zur Theorie der Wirbelstabilisierung in einem zylindrischen Lichtbogen

Contrarily to well known cylindrical, whirl-stabilized electric arcs with rotating walls or with nearly tangential gas inlets, we discuss a new geometry of an electric arc for producing a whirl around the axis. These investigations have been performed for transferring the theory to a torus arc in a similar way. By using a numerically calculated temperature distribution the hydrodynamic properties are studied taking into consideration the single-fluid model of plasma physics. The results are compared with our experiments and those of other institutes. They agree well and give hope to a stabilizing effect for an electric arc of this geometry. The analytical distributions of the velocities and the pressure are calculated on the basis of perturbation theory. The results are applied to a nitrogen arc at a pressure of one atmosphere and for a definite set of parameters.     

Korrelationen in einem Rubidiumsystem von einigen hundert Atomen

Molecular-dynamics calculations were carried out for Rubidium in the vicinity of the melting temperature using model systems of 250 and 686 atoms. For the interaction between the atoms a pair potential was used which was obtained by the pseudopotential method. When calculating with 686 atoms it was noted that the system is initially in a quasi-liquid state and changes into the solid state after some 10^?12 sec, in the absence of external influences. The mean-square displacement, the structure factor, the velocity autocorrelation function, and the correlation functions for the magnitudes and the directions of the velocities were calculated and are discussed for both phases.