In a rotating plasma, with co-neutral beam injection (NBI), the Doppler shift of the NBI particles, as viewed in the frame of the plasma, can result in a significant reduction in the beam-driven (Ohkawa) current when the rotation is strong. The correction applies to the toroidal fast-ion current calculated for a non-rotating plasma and is independent of the normal Z eff and electron trapping terms. A simple analyticalmodel is presented to estimate the magnitude of the effect for plasmas with arbitrary toroidal rotation and the conditions where this is important have been identified. This model has been compared to the results from existing Monte Carlo neutral beam codes and found to reproduce their results.
