Kinetic Particle-In Simulations of Transport in a Tokamak Scrape-Off Layer.

The focus of this thesis is the application of particle-in-cell (PIC) simulation techniques to the study of particle and energy transport in the scrape-off layer (SOL) of a tokamak fusion device. The PIC computer code that is used in this endeavor provides a fully-kinetic, self-consistent description of plasma transport in one spatial dimension (along the open magnetic field lines in the SOL) and two velocity components (v_ {|} and v_{ |}). The diverted-tokamak SOL system was modeled with various levels of physical complexity. The most rudimentary system studied, a collisionless bounded plasma-sheath region, was used to investigate the dependence of the potential structure on the source distribution function used to inject plasma into the SOL. The results from this study were in reasonable agreement with the predictions of previously developed analytic theories. The next level of complexity included the effects of Coulomb collisions. Plasma transport in the SOL was modeled over the wide range of collisionality encountered in current and near-term devices. The electron heat conduction flux in these simulations was limited to 11-21% of the free-streaming thermal flux. Finally, the atomic physics processes of charge exchange and ionization were included in the collisional model. These interactions between the charged-plasma and recycled-neutral particles can significantly affect energy transport through the SOL. This complete version of the kinetic PIC model was used to simulate SOL transport for various values of neutral particle density between the low-and high-recycling limits. The electron and ion kinetic energy fluxes to the divertor plate exhibit a marked decrease as the level of neutral particle recycling increases. The performance of the direct implicit PIC code has been determined with regard to the size of the time step Delta t and grid spacing Delta z. Each of the physics packages incorporated into the PIC code has been benchmarked against either available theories or independent numerical models. To demonstrate the code's versatility, plasma confinement in mirror devices has also been modeled, and the results have been benchmarked against those from a bounce-averaged Fokker-Planck code.