Negative hydrogen ion maintenance in small radius discharges: Two-dimensional modeling

The results from a two-dimensional model of hydrogen discharges sustained in a single-chamber small radius plasma source presented in this study show that when the plasma maintenance is nonlocal, the conditions ensuring high concentration of the negative ions are formed by the behavior of the entire discharge structure and, in particular, of the fluxes in the discharge. The traditionally accepted requirements for low-electron temperature and high-electron density formulated based on the locality of the discharge behavior can no longer be employed. The obtained results show strong accumulation of negative ions in the discharge center, which results from their flux in the dc electric field, not from local balance of the ions there.