Development of oxygen ion source with microwave plasma cathode

Abstract

A new type of broad-beam ion source, which is a bucket-type ion source with a microwave plasma (MP) cathode instead of conventional thermionic filaments, has been developed. Producing a high-density plasma in the MP cathode under the electron-cyclotron-resonance (ECR) condition, this cathode has a capability of a high-current electron emission and has a long lifetime (more than 100 h for an oxygen gas). The structure of this cathode is very simple and compact. Rod antennas connected to coaxial lines for introducing the microwave power (2.45 GHz) and a permanent magnet for producing the ECR condition are major components. In the bucket-type ion source with the MP cathode, the high-current ion beams of 230 mA for an argon gas and 132 mA for an oxygen gas in 115 mm diameter have been successfully obtained with excellent uniformity of the ion beam.