@phdthesis{Stark2006,
  author    = {Albrecht Stark},
  title     = {Ion dynamics in magnetized plasmas},
  journal    = {keine Angaben},
  url       = {https://nbn-resolving.org/urn:nbn:de:gbv:9-000080-9},
  year      = {2006},
  abstract  = {In magnetized plasmas the understanding of the plasma dynamics in response to magnetic fluctuations is of particular interest. These fluctuations appear in form of linear and nonlinear wave phenomena and also as a change of the magnetic field topology. In the context of the present thesis the influence of low-frequency electromagnetic waves and topological changes of magnetic fields caused by magnetic reconnection on the ion dynamics was experimentally investigated. In the linear magnetized laboratory experiment VINETA kinetic Alfv{\´e}n waves were excited and identified via detailed measurements of the waves dispersion by means of magnetic fluctuation diagnostics. For the understanding of the dispersion behavior boundary effects and the influence of collisions must be taken into account. The ion velocity distribution function (IVDF) was measured with laser-induced fluorescence (LIF). The standard LIF scheme was extended to obtain phase-resolved IVDFs in case of periodic perturbations. The electrical fields of the linear Alfv{\´e}n waves, which are driven by small amplitude magnetic perturbations, are however usually too small, to significantly influence the ion dynamics. A different situation emerges for a strongly nonlinear excitation scheme: Strong indications for wave particle interaction was found in LIF measurements made on nonlinear Alfv{\´e}nic waves in amplitude modulated helicon plasmas. In the toroidal experiment VTF magnetic reconnection can be driven periodically and under reproducible conditions. These precondition facilitates systematic investigations of magnetic reconnection and its influence on the ion dynamics with LIF. For the first time it was proven that ion heating is a direct consequence of reconnection. Furthermore, it could be shown that this heating is strongly localized at the magnetic X-point, which is the location where reconnection occurs. With time-resolved measurements of the IVDF a causal connection between the reconnection rate and the ion heating could be established. Furthermore, strong non-thermal components of the IVDF were detected, which correlate with the observed ion heating. Numeric simulations, based on a kinetic single particle picture, show a transfer from magnetic energy to kinetic energy of the ions, which is consistent with the experimentally observed rise of the ion temperature.},
  language  = {de}
}