Sufficient cusp magnetic field for designing a novel electron cyclotron resonance ion source

Some have used a cusp modified minimum-B field configuration for designing an electron cyclotron resonance ion source (ECRIS) for 2.45 GHz μ-wave (microwave) frequency. A few ECRIS of this type were tested for >2.45 GHz also but later on converted into the conventional ones because of their poor performance. In this note is an attempt to understand the problems of the old cusp field ECRIS. They are mitigated using a highly permeable midiron disk and negatively biased metal ring and disk in the midplane and at the injection end to design and construct a compact and cost-effective ECRIS of the future.