Browsing by Author "Kersten, H."

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    Abschlußbericht zum Vernetzungsprojekt "Zinkoxidschichten für Dünnschichtsolarzellen", Teilvorhaben: Plasmaanalyse an Sputteranlagen zur ZnO-Deposition
    (Hannover : Technische Informationsbibliothek (TIB), 2005) Wiese, Ruben; Kersten, H.; Hannemann, M.; Hähnel, M.
    [no abstract available]
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    Behavior of a porous particle in a radiofrequency plasma under pulsed argon ion beam bombardment
    (College Park, MD : Institute of Physics Publishing, 2010) Wiese, R.; Sushkov, V.; Kersten, H.; Ikkurthi, V.R.; Schneider, R.; Hippler, R.
    The behavior of a single porous particle with a diameter of 250 μm levitating in a radiofrequency (RF) plasma under pulsed argon ion beam bombardment was investigated. The motion of the particle under the action of the ion beam was observed to be an oscillatory motion. The Fourier-analyzed motion is dominated by the excitation frequency of the pulsed ion beam and odd higher harmonics, which peak near the resonance frequency. The appearance of even harmonics is explained by a variation of the particles's charge depending on its position in the plasma sheath. The Fourier analysis also allows a discussion of neutral and ion forces. The particle's charge was derived and compared with theoretical estimates based on the orbital motion-limited (OML) model using also a numerical simulation of the RF discharge. The derived particle's charge is about 7-15 times larger than predicted by the theoretical models. This difference is attributed to the porous structure of the particle. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
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    Examples for application and diagnostics in plasma-powder interaction
    ([London] : IOP, 2003) Kersten, H.; Wiese, R.; Thieme, G.; Fröhlich, M.; Kopitov, A.; Bojic, D.; Scholze, F.; Neumann, H.; Quaas, M.; Wulff, H.; Hippler, R.
    Low-pressure plasmas offer a unique possibility of confinement, control and fine tailoring of particle properties. Hence, dusty plasmas have grown into a vast field and new applications of plasma-processed dust particles are emerging. There is demand for particles with special properties and for particle-seeded composite materials. For example, the stability of luminophore particles could be improved by coating with protective Al2O3 films which are deposited by a PECVD process using a metal-organic precursor gas. Alternatively, the interaction between plasma and injected micro-disperse powder particles can also be used as a diagnostic tool for the study of plasma surface processes. Two examples will be provided: the interaction of micro-sized (SiO2) grains confined in a radiofrequency plasma with an external ion beam as well as the effect of a dc-magnetron discharge on confined particles during deposition have been investigated.
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    Feasibility of electrostatic microparticle propulsion
    (College Park, MD : Institute of Physics Publishing, 2008) Trottenberg, T.; Kersten, H.; Neumann, H.
    This paper discusses the feasibility of electrostatic space propulsion which uses microparticles as propellant. It is shown that particle charging in a plasma is not sufficient for electrostatic acceleration. Moreover, it appears technically difficult to extract charged particles out of a plasma for subsequent acceleration without them being discharged. Two novel thruster concepts are proposed. In the first one, particles with low secondary electron emission are charged using energetic electrons in the order of magnitude of 100eV. The second concept charges the particles by contact with needle electrodes at high electrostatic potential (∼20kV). Both methods allow the maximum possible charges on microparticles. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
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    Interaction of injected dust particles with metastable neon atoms in a radio frequency plasma
    ([London] : IOP, 2008) Do, H. T.; Kersten, H.; Hippler, R.
    Spatial density and temperature profiles of neon metastables produced in a radio frequency (rf) discharge were investigated by means of tunable diode laser absorption spectroscopy. The experiments were performed in the PULVA1 reactor, which is designed for the study of complex (dusty) plasmas. The line averaged measured density is about 1.5 × 1015 m-3 in the bulk and drops almost linearly in the plasma sheath. The gas temperature is in the range of 370390 K. The flow of metastable atoms in the plasma sheath deduced from the spatial density distribution is dominated by the flow towards the rf electrode. The sheath length is supposed as the effective diffusion length in the plasma sheath region. This approximation was used to investigate the interaction of injected particles with the plasma. The observations and estimation provide evidence for a significant interaction between metastable atoms and powder particles which is important for energy transfer from the plasma to the particles. The power per unit area absorbed by dust particles due to the collision of metastable atoms with the dust particle surface is in the range of a few tens of mW m-2.
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    Particles as probes for complex plasmas in front of biased surfaces
    (College Park, MD : Institute of Physics Publishing, 2009) Basner, R.; Sigeneger, F.; Loffhagen, D.; Schubert, G.; Fehske, H.; Kersten, H.
    An interesting aspect in the research of complex (dusty) plasmas is the experimental study of the interaction of micro-particles with the surrounding plasma for diagnostic purposes. Local electric fields can be determined from the behaviour of particles in the plasma, e.g. particles may serve as electrostatic probes. Since in many cases of applications in plasma technology it is of great interest to describe the electric field conditions in front of floating or biased surfaces, the confinement and behaviour of test particles is studied in front of floating walls inserted into a plasma as well as in front of additionally biased surfaces. For the latter case, the behaviour of particles in front of an adaptive electrode, which allows for an efficient confinement and manipulation of the grains, has been experimentally studied in terms of the dependence on the discharge parameters and on different bias conditions of the electrode. The effect of the partially biased surface (dc and rf) on the charged micro-particles has been investigated by particle falling experiments. In addition to the experiments, we also investigate the particle behaviour numerically by molecular dynamics, in combination with a fluid and particle-in-cell description of the plasma. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.