An Optimum Condition of Multipole Field for an ECR-Type Jon Source

Abstract

A beam current including multiply charged ions was maximized by optimizing a plasma generated by ECRF (electron cyclotron range of frequency) microwave discharge in a hexapole-mirror magnetic field. The plasma density exceeded acritical value by one order of magnitude. From calculation of a plasma resonance equation it was disclosed that there exists a resonance zone for the overdense plasma. Experimentally, this plasma was obtained only when a magnetic flux surface involving the resonance zone nests within the plasma vessel.