Experimentelle Bestimmung der Supraleitungsparameter einiger Verbindungen vom β-Wolframtyp aus Magnetisierungsmessungen

A complete analysis of magnetization curves is given for bulk sintered samples of Nb₃Sn with low hysteresis and for finely powdered sintered and melted samples of Nb₃Sn, Nb₃Al, V₃Si and V₃Ga. The Ginzburg-Landau parameterκ and the penetration depthλ of weak magnetic fields is calculated from the temperature dependence of the thermodynamic and upper critical fieldsH _c andH _c2. The slope of theH _c ?T curve is about 360 Oe/°K and approximately the same for all measured samples. There is an extremely high increase of the lower critical fieldH _c1 if the grain size approachesλ. The occurence of field expulsion and partially reversible magnetization curves of sintered Nb₃Sn samples with high sintering temperatures and high pore volumes is explained by means of connections between single grains which have lower transition temperatures.     

Das Abklingen des Plasmas der Impulslaser-Gasentladung in Stickstoff

For a typical laser gas discharge, the concentration and temperature of the most important plasma components at the end of the current pulse are calculated on the basis of given data for the tube radius, gas pressure, and energy input. Relating to a postdischarge time up to 1 s, the deionization, the association of the nitrogen atoms, the deexcitation of metastable molecules and the relaxation of the vibration temperature are investigated by means of simple balance equations. Finally the influence of plasma relicts on the following discharge pulse is discussed.     

Bestimmung der Kernmomente des Ho165 aus der Hyperfeinstruktur des Grundzustandes im Ho I-Spektrum

In an atomic beam magnetic resonance experiment, the hyperfine interaction constantsA andB of the⁴ I _2/15-groundstate of Ho¹⁶⁵ were found to beA=800,58389 (50) MHz,B=?1667,997 (50) MHz. Using an effective value for 〈r ^?3〉, the magnetic moment of the Ho¹⁶⁵ nucleus was calculated to beμ=4·1(4)μ _n . The quadrupolement was determined by use of the 〈r ^?3〉 given byWatson andFreeman. The result isQ=2·4·10^?24 cm².     

Berechnung des Gleichgewichts axialsymmetrischer toroidaler Plasmen aus der Shafranov-Gleichgewichtsbedingung

The presented method is based on an extension of the Goldberger-Adams theorem and on a systematic application of Wick's theorem. The latter leads to combinatorial problems, which in general are complicated but well-fit to be handled by computers. In the two pureJT-casesE-e andT-t the combinatorial problems are simple. In particular in theE-e-case (trigonal) the optical response can be written in a concise analytical form. It is shown further that by means of a one-to-one correspondence of the respective combinatorial problems it suffices to calculate the complete sequence of moments in the strong coupling limit to write down expressions for the optical response with arbitrary coupling, which are exact both in the strong and weak coupling limit.