Effects of magnetic field gradient on ion beam current in cylindrical Hall ion source

The effects of the magnetic gradient on the ion beam current in an end Hall-type ion source with a magnetic mirror field are investigated. In a cylindrical Hall ion source in which a cylindrical magnetic ring other than a regular magnetic pole is shortened and centrally inserted, a mirror magnetic field profile can be formed around the annular anode. A positive-negative variable magnetic gradient is shown experimentally to enhance ionization; the ionization efficiency is substantially affected by the different magnetic gradient. The high ionization results in 60% efficiency in the conversion of discharge current to ion beam current. The experimental results and interpretation of the effects are presented in this paper.