Possibility of medium energy neutral beam injection into stellarator reactor

The energy necessary for neutral particles to penetrate into the plasma center may be of the order of 0.6 -- 1 MeV in the case of a fusion reactor. The conversion efficiency to convert such a high energy ion beam into a neutral beam is extremely small. We study here the case where fast neutral particles are injected so that the ionized fast ions are trapped in helical ripples of the stellarator field. It is shown that the trapped ions can drift into the plasma center even if the energy is of the order of 100 keV. (auth.)