Tomographic methods are used for the investigation of three-dimensional compressible flow fields by means of interferometric methods. A modified algebraic reconstruction technique algorithm is applied. The algorithm proved to give reliable reconstructions from experimentally measured projection data in the case of an unrestricted angular view. The method was used for the reconstruction of density distributions of weakly perturbed supersonic free jets exiting from a deformed Laval nozzle. Even small perturbations of the jet resulted in significant three-dimensional effects. Reconstruction of a multiple system of jets emanating from a sievelike nozzle showed mutual interactions between the constituent jets. For the investigation of unsteady flows a setup for the recording of holographic interferograms was designed. Here, because of experimental restrictions, only a limited angular range of views was accessible. In the context of this limited-view geometry, reconstructions revealed considerable distortions for objects containing steep gradients.
Using monochromatized synchrotron radiation with variable photon energy E i --43.01 ... 43.35 keV, Resonant Raman Scattering (RRS) by Neodymium atoms (K-shell binding energy Bls=43.57keV) was investigated. For the first time the fine structure splitting in a K-L-RRS spectrum due to the energy difference of the L 2 and L 3 subshells was observed. In addition, the first observation of K-N-RRS in the spectrum of scattered photons is reported. The measured double-differential RRS cross sections are, on an absolute scale, in very good agreement with those calculated in the nonrelativistic dipole approximation, modified by relativistic corrections.
Cross section profiles d2a/df2dco ' for Compton scattering of photons by bound electrons are calculated for all subshells of the atom. Results obtained from the form factor approximation and from a relativistic version of the impulse approximation are compared with experimental data for Cu and Pb at a scattering angle of 0=145 ~ and a photon energy of 662keV. The impulse approximation proves to be superior to the form factor approximation and is used to predict cross section profiles for a primary energy of 50 MeV and different scattering angles and charge numbers. It is shown that only for the heaviest atoms and scattering angles below 0= 5 ~ there is a non-negligible contribution of Compton scattering to the elastic peak.
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