A FILAMENTLESS ION-SOURCE FOR MATERIALS PROCESSING

A dual-stage, multiaperture gas ion source with 5 cm beam diameter has been built and characterized. The first discharge stage is a constric ted glow discharge injecting a plasma stream into a discharge cavity s upporting a Penning ion gauge discharge in the low pressure mode. Both discharge stages and ion extraction are fed by a single, grounded pow er supply. This simplifies the electrical setup and reduces costs. Var ious gases have been tested including nitrogen, oxygen, and argon. The ion beam current density is 250 mu A/cm(2), i.e., the beam current is about 5 mA, at an extraction voltage of 3.0 kV and a discharge curren t of 59 mA. Measurements of the ion beam current as a function of vari ous parameters such as the discharge voltage and current, gas flow, an d magnetic field are presented. The source is compact and can be easil y adapted to various materials modification applications in which ion energies of a few keV are required, (C) 1998 American Institute of Phy sics.