A Study on the Design of Full-LTS 18-GHz ECR Ion Source for Heavy Ion Accelerator

An electron cyclotron resonance (ECR) ion source is an essential component of the heavy ion accelerator. The intensity of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of the ECR zone, which is one of the key elements of the ECR ion source. The ECR zone locates in a minimum B field configuration that is created by solenoids and hexapole. For an 18-GHz ECR ion source, hexapole is generally made by a permanent magnet. In this paper, a low-temperature superconductor (LTS) magnet was used instead of a permanent magnet because its cost becomes higher and higher, and finally, the mechanical stress of hexapole would be enhanced. First, the hexapole-in-solenoid system and the solenoid-in-hexapole system with several numbers of solenoid coils were analyzed. Then, the most appropriate arrangements for ECR systems were selected. The total length of LTS wire was minimized with the ECR zone volume and the maximum magnetic field in hexapole, respectively, using the evolution strategy method. Finally, the optimized design for a full-LTS 18-GHz ECR ion source was presented.