Tokamaks magnetically confine toroidal plasmas in the toroidally axi-symmetric magnetic field. This axi-symmetry cannot be perfect due to imperfections in the surrounding magnets and conductors, which produce toroidally non-axi-symmetric magnetic field. Physics of 3D tokamak has been of great importance in the recent fusion plasma research, since demonstration of control of edge localized modes and toroidal rotation with externally applied 3D field. The 3D magnetic field fundamentally changes charged particle orbit motions to modify transport and stability of tokamak plasmas, and can significantly degrade or improve the machine performance. This talk will introduce transport physics of tokamak plasmas in the presence of 3D magnetic field. Modification of thermal ion transport by 3D field will be discussed with a focus on toroidal momentum transport using guiding center particle simulation. 3D field effect on transport of fast ions supplied by neutral beam injection heating will be discussed using full orbit particle simulation.
