Toroidal field ripples of tokamaks resonate under certain conditions with the cyclotron motion of charged particles streaming along the magnetic field lines. This resonance may yield the evolution of the magnetic moment, a good adiabatic invariant of the motion in magnetic fields. The equation of motion for the magnetic moment is discretized to a mapping which describes the evolution of the magnetic moment across the successive resonances. On the basis of the mapping, derived the linear stability of the motion in the phase space and the diffusion constant of the magnetic moment when the motion becomes stochastic. (author).
Tanaka, Masatoshi 
- Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment