High Current Audio Frequency (Ion/Electron) Source

Simple technique is used for production of high ion / electron current from an Audio Frequency (AF) (10 - 50 kHz) discharge source. Small size plasma bottle (ϕ = 30 mm, L = 35 mm) with capacitive electrode of AF antenna immersed inside it. The source is working at high discharge pressure ~ 0.2 Torr., without the need of high vacuum system. The extraction system is concentric hemisphere electrodes which allow self-beam focusing by adjusting the beam minimum size and its position from the source exit. The ion species used are nitrogen and argon, the discharge power (100 - 500 W) and the extraction voltage is (100 - 600 V). The AF discharge shows a high discharge cross-section of ionization at certain frequency of the AF supply. The behavior of the AF discharge acts similar to the D.C. discharge explained by known Paschen's curve. The maximum extracted Ar electrons and ions currents are 10 and 2.4 mA respectively, while for Nitrogen are 12.5 and 2.7 mA. Beam simulation by SIMION program shows a good agreement with the analytical study of the hemi-sphere electrodes extraction system.