Atomic processes, cross sections, and reaction rates necessary for modeling hydrogen negative‐ion sources and identification of optimum H− current densities

The principal electron excitation cross sections for vibrational excitation in a hydrogen discharge are reported. In the first chamber of a two‐chamber hydrogen negative‐ion‐source system subject to the beam‐line constraint of a maximum gas pressure, the density of vibrationally excited molecules reaches an asymptote for increasing discharge current or the equivalent fast electron density. Operating near this first‐chamber asymptote, there exists a spatially dependent maximum negative‐ion density in the second chamber. With the extraction grid placed at this maximum the optimum performance of a hydrogen‐based system is determined. This optimum performance provides a criterion for the selection of differing source types for fusion applications.