Numerical Analysis of Proton Ratio in a Hydrogen Ion Source for Neutral Beam Injector

One requirement for high current ion sources for use in further heating of fusion plasma is the production of ion beams with high proton fractions. In this paper, ion species in a hydrogen plasma are calculated systematically as a function of plasma parameters, i.e. electron density, electron temperature, pressure of hydrogen gas and plasma volume. Furthermore, in the present analysis, the recombination factor for hydrogen atoms at the wall surface of vacuum vessel is treated as another plasma parameter. Results have been obtained for the case of bucket type ion source and compared with published experimental data. The most remarkable point is that ion species ratio depends strongly on the recombination factor, and the proton ratio increases with decreasing the recombination factor.