SPACE AND VELOCITY DISTRIBUTIONS OF FAST IONS IN MAGNETICALLY CONFINED PLASMAS

General expressions in terms of the orbit-averaged distribution functi on are obtained for local characteristic quantities of fast ions, such as the velocity distribution, particle and energy density, and power deposition. The resulting expressions are applied to the case of a ver y peaked production profile of fast ions, characterized by particularl y strong orbital effects. It is shown that in this case the radial pro files of the fast ions can be significantly different from the source profile, being, for example, strongly non-monotonic. The analysis is c arried out for a straight as well as for a tokamak magnetic field. It is predicted that marginally co-passing and semi-trapped particles (i. e. particles that are trapped in only one azimuthal direction) can be transformed to trapped and circulating particles due to electron drag. Collisional constants of motion are obtained.