This thesis presents the essential parts of the first principles theory that is used to describe the evolution of minority particle populations in tokamak plasmas. Also, numerical models specific for Monte Carlo studies of fast ion transport are introduced, and the transport of alpha particles due to magnetohydrodynamical (MHD) activity is investigated in ITER scenarios. The thesis starts by introducing the very idea behind Monte Carlo simulations: an explicit proof of the connection between a Fokker-Planck equation and stochastic processes is given. This connection is then used to provide the stochastic differential equation for a charged particle that describes both the Hamiltonian and collisional motion of the particle in a plasma. Although following stochastic trajectories of charged particles and constructing the distribution functions a statistical average allows first principle solutions of the corresponding kinetic equation, the method is computationally very expensive. To offer numerically more attractive approach, the theoretical part is continued by introducing the guiding center transformation of the particle kinetic equation. The transformation is discussed in detail, and derivation of the guiding center motion is given explicitly. The theoretical work and the fast ion specific models are then implemented to construct a revieved version of the numerical Monte Carlo tool called ASCOT. As an application, the code is used to study MHD induced alpha particle transport in ITER. The results for the transport studies confirm that the neoclassical tearing modes would not endanger the integrity of the plasma facing components. However, it is noticed that the transport due to toroidal Alfvén eigenmodes could significantly change the power deposition from the alphas to the bulk plasma.
|Publication status||Published - 2014|
|MoE publication type||G5 Doctoral dissertation (article)|
- Monte Carlo-method, tokamak, plasma