The Scaling AnalySiS Of a Beam Drlven Current In

A beam-driven current observed in CHS neutral beam injection (NBI) experiments is analyzed and reported in this paper. Five hundred and thirty NBI discharges of CHS were analyzed to investigate the behavior of the beam-driven current in detail. The observed beam-driven current was compared with a calculated Ohkawa current using Gaffey's solution to the fast-ion Fokker-Planck equation. The scaling law of the beam-driven current agrees with the theoretical prediction with regard to power, density, and magnetic field dependence, but there is a significant difference with regard to the dependence on the electron temperature. The observed value of the current is smaller than that of the theoretical prediction especially for high temperature discharges. Possible mechanisms causing such a difference are discussed.