Stabilization of the Alfvén wave instability in a two-component tokamak

The stabilization of the Alfvén wave instability in a two-component tokamak is investigated theoretically. It is assumed that the instability is caused by fast ions which form in the tokamak when fast neutral atoms are injected into it. Dissipation through collisions with trapped electrons is considered to be a stabilizing factor. The method developed by Timofeev for considering initial perturbations is employed. It is shown that the influence of dissipation through collisions with trapped electrons on the "local" growth rate of the instability of an ion beam is insignificant in cases of practical interest. Such collisional dissipation is also insignificant as regards the evolution of initial perturbations if the thermal spread of the beam is not too great. It can, however, play an appreciable role in the case of very diffuse beams. This opens up the possibility of suppressing Alfvén instability by injecting into a tokamak neutral atoms with a broad energy spectrum.