Performance characteristics of a broad-beam, low-energy, atomic-ion plasma source

Summary form only given. An investigation in the framework of an on-going program to develop broad-beam (>100 cm/sup 2/), low-energy (30-100 eV), magnetically filtered atomic-ion plasma sources for use in space and ground-based applications is discussed. The plasma source consists of an open-ended, line-cusp discharge chamber with an interaction region that is bounded by a magnetic filter and a high-transparency grid at the source´s exit plane. An atomic-ion plasma diffuses from the source and fills the vacuum chamber volume. It has been demonstrated that the source can produce greater than 95% atomic-ion concentrations of nitrogen or oxygen. It was measured how the source´s performance is affected by several parameters: the background neutral-gas pressure, the grid bias voltage, the discharge voltage, and the discharge current. An ExB probe was used to measure the relative fraction of atomic ions to molecular ions, and a multiple-grid energy analyzer was used to measure the ion energy distribution and how it is influenced by the discharge voltage. The authors documented the position dependence of the ion fraction and ion energy, and used the results to infer a measure of the atomic-ion recombination.