Sheath formation criterion and ion flux for a non-Maxwellian plasma containing negative ions

The criterion for the formation of a stable ion sheath is considered for an arbitrary electron energy distribution function F(E) to estimate the ion flux from a plasma containing negative ions. The cases of Maxwellian, Druyvesteyn and other energy distributions are discussed for comparison. As an application of the present method, the diagnostic of negative ion containing plasmas by using the kinetic energy distribution and probe characteristics is considered. The range of applicability of the present model is given. As another application, the ion current densities extractable from an ion source are estimated.