Minority ion cyclotron heating can produce energetic ions with banana orbits that are finite compared with the minor radius of a tokamak. The radial transport of the fast ions in the presence of Coulomb collisions results in a radial current and a corresponding J×B torque density on the bulk plasma. Collisions between the minority ions and majority ions provides and additional frictional torque that adds to or opposes the magnetic torque. Our study uses a code which follows the particle drift

more »

... ajectories in a tokamak geometry under the influence of rf fields and collisions, modeled with an rf-quasilinear operator and a Monte-Carlo operator, respectively. It is shown that when the regions of negative and positive torque density are spatially separated, a finite central rotation velocity can result even when the volume integrated torque density is small. This is consistent with the results of Perkins [F.W. Perkins, et al., "Generation of Plasma Rotation in a Tokamak by Ion-Cyclotron Absorption of Fast Alfvén Waves," to appear in Phys. Plasmas, 2001], that uses a different approach. A physical picture emerges explaining the co-and counter-rotation with low-and high-field resonance respectively as a consequence of finite orbit width. The model also provides details of the rotation profile when ions are continuously being heated and slowed down in steady-state. Qualitative comparison with recent JET results will be discussed.