The variations of plasma parameters on the boundary conditions, especially potential, of plasmas were measured in an inductively coupled plasma source developed to generate a hyperthermal neutral beam. Hyperthermal neutrals can be produced by Auger neutralization when ions with low energy are neutralized by impinging on a metal surface called a reflector. However, the reflector is a significant source of ion drain when it is biased to a negative potential. The plasma potential can be negative with respect to the grounded chamber potential while the reflector is negatively biased, but other plasma parameters, namely density and temperature, are not sensitive to the reflector bias. If the electron loss current into the chamber wall is governed by the space charge limited current law, sustainment of the plasma with a negative potential can be explained in terms of the charge balance equations for quasineutrality.

http://dx.doi.org/10.1063/1.2786069