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Author: Bundesmann, C. × Has files: Yes ×

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    Advanced Electric Propulsion Diagnostic Tools at IOM
    (Amsterdam [u.a.] : Elsevier, 2017) Bundesmann, C.; Eichhorn, C.; Scholze, F.; Spemann, D.; Neumann, H.; Scortecci, F.; Leiter, H.J.; Holste, K.; Klar, P.J.; Bulit, A.; Dannenmayer, K.; Amo, J. Gonzalez del
    Recently, we have set up an Advanced Electric Propulsion Diagnostic (AEPD) platform [1], which allows for the in-situ measurement of a comprehensive set of thruster performance parameters. The platform utilizes a five-axis-movement system for precise positioning of the thruster with respect to the diagnostic heads. In the first setup (AEPD1) an energy-selective mass spectrometer (ESMS) and a miniaturized Faraday probe for ion beam characterization, a telemicroscope and a triangular laser head for measuring the erosion of mechanical parts, and a pyrometer for surface temperature measurements were integrated. The capabilities of the AEPD1 platform were demonstrated with two electric propulsion thrusters, a gridded ion thruster RIT 22 (Airbus Defence & Space, Germany, [13]) and a Hall effect thruster SPT 100D EM1 (EDB Fakel, Russia, [1], [4]), in two different vacuum facilities.
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    Electronic transitions and dielectric function tensor of a YMnO3 single crystal in the NIR-VUV spectral range
    (London [u.a.] : Royal Society of Chemistry, 2014) Schmidt-Grund, R.; Richter, S.; Ebbinghaus, S.G.; Lorenz, M.; Bundesmann, C.; Grundmann, M.
    We present optical properties in the near-infrared to vacuum-ultraviolet spectral range of hexagonal YMnO3. The high-quality (110)-oriented bulk single crystal was grown by the optical floating zone technique. We have determined the tensor of the dielectric function by means of Mueller matrix ellipsometry in the wide spectral range (0.5-9.15) eV. For the spectral range below 5.4 eV, we present much more precise data compared to previous reports. For higher energies no experimental reports were given previously. The experimental dielectric function of YMnO3 agrees generally with theoretical calculations. We found the well known transitions involving hybridized oxygen-Mn states and Mn-3d states to be spectrally localized with a homogeneous Lorentzian lineshape. At energies above these transitions, we observe pseudo-transparent points where for each of the principal diagonal elements of the dielectric function tensor the imaginary part approaches zero but at different photon energies. These are followed at the onset of the high-absorption spectral range by parabolic direct band-band transitions which have not been reported so far.
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    Modelling of a radio frequency plasma bridge neutralizer (RFPBN)
    (Amsterdam [u.a.] : Elsevier, 2017) Scholze, F.; Eichhorn, C.; Bundesmann, C.; Spemann, D.; Neumann, H.; Bulit, A.; Feili, D.; Gonzalez del Amo, J.
    A performance model of a radio frequency plasma bridge neutralizer was developed to calculate the electrical parameters and optimize the neutralizer design. Minimization of power losses and gas consumption, and a maximization of the neutralizer lifetime and the reliability of the system are requirements of all electric propulsion concepts and strongly determine their future application. The requirements of the neutralizer depend on mission profiles.