Study of H^- production in DC H^- source of medical cyclotron

A filament driven multi-cusp negative hydrogen ion source has been developed for proton cyclotrons. In order to increase the H^- beam current, the dependences of H^- beam current on various design/operating parameters has been studied experimentally and numerically. In this paper, the effects of arc-discharge voltage and current on H^- production via the volume production process are investigated by three-dimensional kinetic modeling of electrons in the source plasma and zero-dimensional rate equations. This numerical analysis reproduces the experimental results of H^- beam current dependence on the arc-discharge condition, and also gives reasonable explanations for their characteristics.