Fusion reactivities and power multiplication factors of beam-driven toroidal reactors with both D and T injection

Key reactor parameters of intensely beam-driven toroidal plasmas with 50:50 D-T composition maintained by neutral-beam injection of both D and T, together with plasma re-cycling, are determined. The deuterons and tritons are injected with equal intensity and velocity. This mode of operation is most appropriate for high-duty-factor, high-power-density operation, in the absence of pellet injection. The velocity distributions of energetic D and T ions are calculated from a relatively simple slowing-down model, but include a tail above the injection velocity that results from energy diffusion. Fusion power multiplication Q and fractional tritium burn-up are determined from fusion reactivities calculated for beam-target, hot-ion, and thermonuclear reactions. For conditions where Q approximately 1, beam-target reactions are dominant, but reactions among the hot ions contribute substantially to the total reaction rate when nsub(hot)/nsub(e)>approximately 0.2. To maintain the bulk-plasma temperature at progressively smaller nsub(e)tausub(E), it is necessary to continuously increase nsub(hot)/nsub(e), so that reactions among energetic ions serve to maximize the Q-value and power density in low-nsub(e)tausub(E)-driven operation. (author)