Generation of Plasma Rotation in a Tokamak by Ion-Cyclotron Absorption of Fast Alfvén Waves

A mechanism is proposed and evaluated for driving rotation in tokamak plasmas by minority ioncyclotron heating, even though this process introduces negligible angular momentum. The mechanism has two elements: First, angular momentum transport is governed by a diffusion equation with a non-slip boundary condition at the separatrix. Second, Monte-Carlo calculations show that energized particles will provide a torque density source which has a zero volume integral but separated positive and negative regions. With such a source, a solution of the diffusion equation predicts the on-axis rotation frequency Ω to be Ω = (4qmaxW J* ) eBR3a2ne(2π)2)-1(τM/τE) where |J*| ≈ 5-10 is a nondimensional rotation frequency calculated by the MonteCarlo ORBIT code. Overall, agreement with experiment is good, when the resonance is on the low-field-side of the magnetic axis. The rotation becomes more counter-current and reverses sign on the high field side for a noslip boundary. The velocity shear layer position is controllable and of sufficient magnitude to affect microinstabilities.