A 13.56 MHz radio frequency (rf) inductively coupled multicusp ion source has been developed for producing an intense argon ion beam with current density in excess of 30 mA cm^-2 . The source chamber is a 10 cm diameter aluminum cylinder surrounded by 20 rows of 3.5 kG Sm-Co₅ magnets which form a longtitudinal line-cusp field configuration. The rf antenna coil, placed inside the source chamber, is made of a braided wire threaded through a 2 turns pyrex tube 6 cm in diameter to prevent electrical leakage and ion sputtering. A 10:1 turns-ratio matching transformer is used to match the 50 output impedance of the rf generator to the impedance of the plasma load.

Preliminary measurements were carried out with single and 4-hole aperture using argon gas. For a single hole extraction with pressure at 5 mTorr and rf power at 500 W, the ion current density was 27 mAcm^-2 . With the same operating condition, the current density was about 25 mAcm^-2 for a 4-hole extraction system.