Simulation study of toroidal flow generation of minority ions by local ICRF heating

The toroidal flow generation of minority ions by the local ion cyclotron range of frequencies (ICRF) heating is investigated in a tokamak plasma by applying the GNET code, which can solve the drift kinetic equation in the 5-D phase space. An asymmetry of velocity distribution function in the parallel direction is found and two types of toroidal averaged flow of minority ions are observed. One is the sheared flow near the RF power absorption region depending on the sign of k_∥, and the other is the toroidal flow, which is larger than the previous one, independent of the sign of k_∥. It is found that the k_∥-sign-independent toroidal flow is generated by the net toroidal motion of energetic tail ions and that the k_∥-sign-dependent flow is related to the mechanism proposed by Ohkawa. (author)