Compact electron cyclotron resonance ion source with a permanent magnet

Abstract

A new compact electron cyclotron resonance ion source that uses a magnetic mirror field and a divergent magnetic field to generate high-density and multicharged ions has been developed. A cylindrical permanent magnet is utilized to produce those magnetic fields. Excited electrons are effectively confined in the mirror field near the exit of the plasma chamber, making it possible to generate high-density and multicharged ions. The generated ions are transported near the center axis and a plasma stream is formed along the divergent magnetic field. A plasma chamber with a diameter 4 cm smaller than the cutoff size (7.2 cm for 2.45 GHz) and a two-layer microwave window are used to fashion the compact structure and to couple microwaves with high-density plasma. The plasma stream is highly directional (plasma stream diameter ∼1.8 cm), and high ion saturation current densities of 18 mA/cm2 (Ar gas) are achieved 12 cm downstream at a low microwave power of 200 W. Moreover, a high Ar2+/(Ar++Ar2+) ratio of above 50% is obtained.