Self-consistent Simulation of Torque Generation by Radial Current due to Fast Particles

The generation of the toroidal rotation due to the radial current torque induced by the charge separation is studied by using one-dimensional multi-fluid transport code TASK/TX. Taking account of the effect of the drift orbit, the charge separation occurs as long as trapped ions are generated, typically by near-perpendicular NBI. Coupling the TASK/TX code with the Orbit-FollowingMonte Carlo code OFMC, we have reproduced the toroidal rotation driven by the radial current by the near-perpendicular NBI with varying its vertical injection (poloidal) angle and clarified that the horizontal NBI drives the toroidal rotation most efficiently. By utilizing the radial current torque, we have elucidated that in a steady state the toroidal rotation is determined by the balance among the torque, the viscosity, the friction with neutrals and the loss of momentum due to charge exchange.