Inward diffusion of Tokamak-trapped particles by slow magnetic pumping

Particle diffusion in a Tokamak configuration under the influence of a very slow magnetic compression wave is studied. The plasma is assumed to be in regime I of Galeev and Sagdeev. The wave interacts irreversibly with trapped particles only and induces a diffusion of these particles. Inward diffusion for a given species takes place if the wave propagates around the major axis faster than the diamagnetic motion of the trapped particles of this species. By using two waves with proper phase velocities, one of which has a preferential coupling with electrons and the other with ions, ambipolar inward plasma diffusion may be achieved. In typical reactor conditions, it is possible to cancel out the neoclassical particle diffusion using magnetic perturbations less than one percent of the static field at frequencies in the kHz-range.