Plasmadiagnostik einer Azetylen-Sauerstoff-Flamme mit Mikrowellen und Magnetfeld

In order to determine the electron-molecule collision frequency in an acetylene-oxygen flame (burning within aX-band wave-guide) the decrease of microwave attenuation caused by an increasing magnetic field is being measured. It is shown that this decrease is equivalent to the wellknown high pass character of a plasma. The small attenuation is enlarged by using a Perot-Fabry type waveguide resonator. Nothing has to be known about its properties, since relative attenuation data are used for evaluation only. For the same reason no knowledge of electron concentration is necessary. The collision frequency value is exact within 4%, which is sufficient for excluding Coulomb collision interaction. The comparison with data in the literature is satisfying only, if the collision model of an electron induced dipol is accepted. With this and a flame temperature of about 3350 °K the collision frequency amounts to 179±7 GHz.     

Direkte Konzentrationsabhängigkeit der Fluoreszenz einer Haupt- und einer Nebenlinie des Rubins

The concentration dependence of theR-lines of ruby shows three characteristic regions: The first has the expected linear increase of emission intensity with increasing concentration; the second shows a weaker increase than linear and is explained by the assumption, that energy is distributed more to nebenlines; the third shows a rapid decrease of the emission as is expected for quadrupole-quadrupole interaction between the active atoms. The emission of theN ₂-line of ruby increases nearly quadratically with increasing concentration and decreases in the third region as fast as theR-lines.     

Grundlagen der absoluten Energiedosismessung von Quanten- und Elektronenstrahlung bis 50 MeV

Die Energiedosis wird heute als die wichtigste dosimetrische Große angesehen. Für sehr viele Anwendungszwecke ionisierender Strahlung gibt es einen einfachen Zusammenhang zwischen dieserGröße und der beobachteten Strahlenwirkung. Ausgehend von der Definition wird die Messung der Energiedosis bei Sekundärelektronengleichgewicht und bei Fehlen dieser Voraussetzung behandelt. Zur Absolutbestimmung der Energiedosis – wobei zugleich auch noch die für ein Standardverfahren erforderliche Genauigkeit erreicht wird – kommen gegenwärtig vor allem Kalorimeter, Ionisationskammern sowie chemische Dosimeter in Frage. Die genannten Verfahren werden kurz behandelt, die Anforderungen an ihre Realisierbarkeit erläutert. Auf Übergangslosungen, die für Elektronen- bzw. Quantenenergien größer ca. 3 MeV anwendbar sind, wird verwicsen.     

Phonon-Resonanzstreuung und Wärmeleitung in einer Silizium-Korngrenze

The thermal conductivity of a grain-boundary in silicon bicrystals has been measured in the temperature range from 12°K to 150°K using a newly developed method. The analysis of the experimental results shows that the thermal conductivity is governed by two scattering processes: the acoustical mismatch of both crystal halves and the resonant scattering of the phonons by impurity atoms of the grain boundary. A new method is thereby presented for the direct observation of phonon resonant scattering.     

Ionisierung von Atom- und Molekularstrahlen mit einer Plasma-Ionenquelle

A method for ionizing atomic and molecular beams is described, in which use is made of a space charge compensated plasma ion source of the Duoplasmatron type. In such a device the ionization yield (ionization and extraction efficiency) can be increased considerably as compared to that in conventional electron bombardment ionizers. The maximum yield of H ₂ ⁺ -ions from a H₂-molecular beam was 3.7%. Further results are contained in the Table.     

Grundlagen einer nichtlinearen Stabilitätstheorie der stationären Zustände isothermer elektrischer Netzwerke

To apply the stability criterion given by Schlögl, we obtain some new macroscopic test functions and determine the conditions which make them globally monotonous and concave. As an example we derive the thermodynamic test function of an isothermal electrical network which may consist of generators, nonlinear reactances, and nonlinear resistances. Finally the temporal development of this test function (which is decisive for the criterion mentioned) is calculated for arbitrary network topology.