PRODUCTION OF IONS IN OPEN-ENDED REGION OF COAXIAL-TYPE MICROWAVE CAVITY

Characteristics of a microwave planar magnetron ion source are described. This source, using a tuned coaxial-type cavity which excited the plasma at the end of the coaxial line, is able to produce a 100-mm-diameter by 20-mm-thick plasma disk that is well matched, stable, and allows continuous operation over a wide range of gas pressures. The isotropic microwave propagation from the surface of the magnetized plasma column to the center is one of the most effective coupling methods to obtain a high-density disk-like plasma. Argon ion current densities of 20-50-mu-A/cm2 have been obtained at energies ranging from a few to 70 eV. The beam uniformity is +/- 2% within a diameter of 5 cm. This new source has the potential to produce low-energy broad-beams.