Monte Carlo simulation of negative ion production in the negative hydrogenion source

Two Monte Carlo simulation codes: (a) neutral transport code and (b) negati ve ion (H-) transport code, have been developed to understand transport phe nomena in negative ion sources. In the neutral transport code, Boltzmann eq uations for hydrogen molecules (H-2) and atoms (H) are solved. Three dimens ional (3D) spatial distributions of H-2, H, and H- production are obtained for a tandem negative ion source. The volume production of H- is limited to the area around the gas inlet in the first chamber and near the plasma gri d in the second chamber. On the other hand, distribution of H- surface prod uction is shown to be almost uniform over all the plasma grid surface. In t he negative ion code, H- trajectories are calculated by numerically solving the 3D equation of motion for H- ions. The effects of the magnetic filter on the extraction probability of surface produced H- ions are mainly studie d. The dependence of the extraction probability on the field strength is sm all. (C) 2000 American Institute of Physics. [S0034-6748(00)52802-0].