A Particle-In-Cell Gun Code for Surface-Converter H- Ion Source Modeling

We present the current status of a particle-in-cell with Monte Carlo collisions (PIC-MCC) gun code under development at Los Alamos for the study of surface-converter H- ion sources. The program preserves a first-principles approach to a significant extent and simulates the production processes without ad hoc models within the plasma region. Some of its features include: solution of arbitrary electrostatic and magnetostatic fields in an axisymmetric (r,z) geometry to describe the self-consistent time evolution of a plasma; simulation of a multi-species (e-,H+,H2+,H3+,H-) plasma discharge from a neutral hydrogen gas and filament-originated seed electrons; full 2-dimensional (r,z) 3-velocity (vr,vz,vφ) dynamics for all species with exact conservation of the canonical angular momentum pφ; detailed collision physics between charged particles and neutrals and the ability to represent multiple smooth (not stair-stepped) electrodes of arbitrary shape and voltage whose surfaces may be secondary-particle emitters (H- and e-). The status of this development is discussed in terms of its physics content and current implementation details