Finite orbit width effects on fast ion distributions and stability of TAEs in tokamaks

Space and velocity distributions of fast ions in tokamaks, which are strongly affected by orbital motion, are found. The orbit transformation of fast ions due to electron drag is predicted. A new general expression for the growth rate of instability on toroidal Alfven eigenmodes is obtained and applied for the analytical study of special cases, e.g. for the instability excited by trapped particles with Δrb >> Lw, Δrb and Lw being the banana width and the width of wave localization, respectively. The influence of finite Δrb on the instability through a non-disturbed distribution function is investigated. (author). 14 refs, 3 figs