Metal ion source using rf discharge combined with sputtering

An ion source capable of producing a wide variety of ion species from elemental materials is described. Ion beams of metals can be produced by sputtering a disk, made of the materials to be ionized, placed on the cathode. In order to raise the rate of ionization of the sputtered materials an rf discharge is superimposed on the dc sputtering. Ions of refractory metals, such as Nb, can be easily produced without using halides.