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 constricted glow discharge injecting a plasma stream into a discharge cavity supporting a Penning ion gauge discharge in the low pressure mode. Both discharge stages and ion extraction are fed by a single, grounded power supply. This simplifies the electrical setup and reduces costs. Various 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 current of 59 mA. Measurements of the ion beam current as a function of various parameters such as the discharge voltage and current, gas flow, and magnetic field are presented. The source is compact and can be easily adapted to various materials modification applications in which ion energies of a few keV are required, (C) 1998 American Institute of Physics.