Design of the magnetic system for an electron cyclotron resonance ion source based on a novel "volume-type" concept

Abstract

Based on a flat magnetic field to confine an electron cyclotron resonance (ECR) plasma. a "volume-type" ECR ion source proposed in recent years has been considered in the present work. With computational studies employing a two-dimensional POISSON code. we designed a magnetic system to realize such a "volume-type" ECR ion source in resonance with a microwave frequency of 2.45 GHz. Our ECR ion source consists of two solenoids for axial mirror fields and six permanent NdFeB magnets for radial multicusp fields. Iron yokes are added to create the flat central field necessary to achieve the "volume-type" ECR plasma. These iron yokes are removable so that our ECR ion source can be configured as a conventional minimum-B-type source. The resonance volume of the present "volume-type" ion source is found to be similar to 200 times as large as that of the conventional minimum-B ion source. Owing to this large and on-axis ECR volume, the "volume-type" ECR ion source proves to be much more effective than the conventional minimum-B ion sources in producing highly charged ion beams.