Neoclassical formula for neutral beam current drive

A new analytic formula for the figure of merit for beam current drive j/p_b is developed in which neoclassical corrections for both ion current and beam induced electron current are incorporated. Small additional correctors for fast ion energy diffusion and charge exchange loss are also introduced. The present formula for j/p_b is based on a circular plasma. The formula is, however, also applicable to a non-circular plasma. With this new formula, the value of j/p_b can be evaluated without solution of the bounce averaged Fokker-Planck equation. One of the applications of the formula is to use it in a self-consistent current drive analysis in combination with MHD and/or transport analysis. In the paper, the formula is used to investigate the various parametric dependences of j/p_b.