Modelling for Production of Multicharged Ions in ECR Source

Abstract

Fundamentals of the ECR (electron cyclotron resonance) multiply charged ion source have been experimentally studied with a tandem-type mirror field configuration using low-frequency microwaves (2.45 GHz). By differential pumping, it is possible to sustain discharge in extremely low gas pressures, where multicharged ions can be efficiently produced. A model is proposed to enable investigation of charge-state distribution of argon ions in a plasma and extracted ion currents. The model includes processes of cumulative ionization, recombination, and charge exchange with neutral particles. Ion confinement times depending on the charge state are also included in the consideration of atomic collision and ion diffusion in the direction along the magnetic field ( z -axis). The calculations, which take account of charge exchange with neutral particles, are consistent with experimental results. Critical comparison between the data and these calculations suggests that high-temperature electrons are essentially important for multicharged ion production.