A wide-aperture source of oxygen ions with a hollow cold cathode and magnetic multicast

A gas-discharge source of oxygen ions is described. The source contains an anode and a hollow cold cathode with one extracting grid (extractor) placed at the opposite end to the anode. The hollow cathode has three multicast m agnetic systems of permanent polarity. The first system is placed inside th e cathode near the anode, the second system is situated outside the cathode opposite to the first one, and the third system is placed below the second one near the extractor surface. Like poles of the first and second magneti c systems are directed towards each other. The second and third systems hav e poles of similar orientations. Using this source, a beam of oxygen ions w ith a current density of up to 0.5 mA/cm(2) and nonuniformity of <5% was ob tained across a 200-mm-diameter area at a distance of 120 mm from the face of the ion source. The source offers the following optimum performance char acteristics: a discharge current of 0.4-1.2 A, oxygen flow rate of 9-12 cm( 3)/min, and extracting voltage of 400-600 V. No limitations were revealed o n the service life of a source operating in optimal modes.