Analytic representation for parallel flow of hot ions produced by tangential neutral beam injection

Tangential neutral beam injection deposits momentum in a fusion plasma, which produces macroscopic flow of bulk particles. Concurrently, equilibrium distribution of hot ions produced by the injection is determined by collisions with the bulk particles. Through these processes, macroscopic flow of hot ions can be produced. Effects of the flow of hot ions have not been focused on since their inertial force is thought to be much smaller than the bulk one due to smallness of density of hot ions. In this study, we derive an analytic representation for parallel flow of hot ions. From the analytic representation, we find that amplitude of the parallel flow is determined by three parameters, injection speed, injection pitch angle, and electron temperature. Also we find that the inertial force of hot ions is not negligible even if the density of hot ions is much smaller than that of bulk ions. (author)