Three-dimensional particle-in-cell simulations of gap crossings in castellated plasma-facing components in tokamaks

This paper presents first 3D particle-in-cell simulations of castellated plasma- facing components (PFCs) in tokamaks. Special focus is given to crossings between poloidal and toroidal gaps where elevated heat loads are expected to occur. Localized heat loads can potentially lead to a damage of the tiles. This paper presents results of a full 3D3V code SPICE3, which allows to simulate a more realistic geometry of the tiles including the gap crossings and includes the complete ExB drift, which could not be simulated in 2D. The results of self-consistent simulations show that the crossing acts as a transport channel for electrons, allowing them to enter the plasma shadowed region in poloidal gaps. As a consequence, the potential near the gap entrance is modified allowing more ions to flow deep i pard