@phdthesis{Slaby2018,
  author    = {Christoph Slaby},
  title     = {Gyro-kinetic simulations of tokamaks and stellarators including collisions},
  journal    = {Gyro-kinetische Simulationen von Tokamaks und Stellaratoren unter Ber{\"u}cksichtigung von St{\"o}{\"s}en},
  url       = {https://nbn-resolving.org/urn:nbn:de:gbv:9-opus-26268},
  pages     = {195},
  year      = {2018},
  abstract  = {This dissertation focusses on the numerical modelling of resonant destabilization of Alfv{\´e}n eigenmodes by fast ions in fusion plasmas. It especially addresses non-linear simulations of stellarator plasmas in which particle collisions are retained. It is shown that collisions are required for a realistic description of Alfv{\´e}n waves in plasmas relevant to nuclear fusion. We start by carefully verifying the implementation of the collision operators into the electromagnetic version of the gyro-kinetic delta-f particle-in-cell code EUTERPE. After these initial benchmarks are completed successfully, the code is in a position to be applied to realistic tokamak and stellarator scenarios. Since every collision operator needs to fulfil conservation laws, a momentum-conserving version of the pitch-angle scattering operator is implemented. This is in particular important for neoclassical transport simulations aimed at computing flux-surface variations of the electrostatic potential in stellarators. Using the simplified CKA-EUTERPE model (employing a fixed-mode-structure approximation), we perform non-linear simulations in tokamaks and stellarators. We show that the non-linear dynamics of fast-ion-driven Alfv{\´e}n eigenmodes is significantly influenced by collisions. They have the potential to enhance the saturation level and to affect the frequency chirping of the modes. It is thus concluded that collisions play an essential role in determining Alfv{\´e}n-eigenmode-induced fast-ion transport - an important issue for future fusion devices. In order to address this issue the CKA-EUTERPE model is extended to evolve multiple modes at the same time. First results of this multi-mode version (which enhances the level of realism of the simulations) are shown in the Appendix of the thesis.},
  language  = {en}
}