Mit Hilfe von auf dem Objekt angebrachten Markierungslinien werden elektronenmikroskopische Präparate (Abdrucke) über die Mitte des Trägernetzes mit einer Genauigkeit von ca. 0,02 mm identisch zentriert. Die beschriebene Methode ist einfach, allgemein verwendbar und ermöglicht das Arbeiten mit einem Minimum an Fehlpräparaten. Elektronenoptische Aufnahmen, welche die gleiche Stelle auf LiF-Monokristallen vor und nach Behandlung zeigen, geben ein Beispiel ihrer Anwendungsmöglichkeit.
The propagation of torsional Alfen waves in a cylindrical plasma is investigated. Superimposed on the plasma are various types of spatially inhomogeneous axisymmetric magnetic fields. Characteristic examples are: in the direction of propagation spatially decreasing, increasing and periodically modulated magnetic fields. The wave lengths are of the same order of magnitude as the characteristic lengths of the inhomogeneities. Strong reflection is observed which depends on wave frequency and strength of the field inhomogeneity. There exists good agreement between experimental results and numerical calculations.
Absorption of magnetoacoustic waves in a high beta plasma The radial propagation and absorption of magnetoacoustic waves (m = 0, kz = 0) in a radially inhomogeneous, high beta plasma column of a theta pinch is investigated both theoretically and experimentally. It is shown, that viscosity is the dominant dissipative mechanism. Power absorption up to 10 MW is obtained, which corresponds to an average heating rate of 5 eV/μsec per particle.
The assignments of fundamental mode frequencies in LiNbO3 determined by IR-and Raman scattering-experiments show some characteristic differences. Comparative frustrated total reflection (FTR) -and Raman scattering-studies were carried out in order to find the origin of these discrepancies. The most serious deviation was due to the fact that in one case the ordinary phonon is observed by Raman scattering whereas the extraordinary mode is recorded only by FTR. It has been shown, on the other hand, that the oblique phonon dispersion technique did not provide arguments for the correct assignments. The main limit of the method is due to the fact that the influence of exciton states on polaritons hitherto is taken into account only by a constant high frequency dielectric 'function' (ε∞). The uncertainty in the choice of a suitable ε∞-value allows fittings of quite diverging sets of experimentally determined fundamental frequencies.