A computational method for optimal triode extraction system of negative hydrogen ion sources

A computational method is developed for the optimized design of a triode extraction system for negative hydrogen ions, aiming at minimizing beam divergence. The method solves the paraxial ray equation across the extraction system and employs the Child–Langmuir law to set the boundary conditions at the plasma meniscus. The model accounts for plasma meniscus curvature and electrostatic lens effects at electrode apertures. Proposed method show good agreement with simulations, with minor discrepancies arising from electrode-edge effects. Parametric studies reveal that beam current, puller voltage, and puller electrode thickness significantly influence the beam divergence. The proposed method provides an efficient tool for preliminary design, bridging simplified analytical models and computationally intensive simulations. Improved potential modeling and inclusion of co-extracted electrons and transverse magnetic fields can further enhance accuracy.