Distortion of the distribution function of weakly RF heated minority ions in a tokamak plasma

An investigation is made of the effect of RF-induced velocity diffusion on the distribution function, f(v), of the heated ion species in minority heating schemes using the fast Alfvén wave. The solution for the distorted distribution function is expressed in a Legendre series from which deviations from isotropy can be assessed. Solutions are found in the limits of high and low velocities and the elongation of the constant f(v) surfaces is also given.