First Test of a Full Length Nb3Sn Sextupole Coil in a Mirror Structure for the FECR Ion Source

The new Nb₃Sn superconducting magnet system for a 45 GHz electron cyclotron resonance (ECR) ion source is under development in the Institute of Modern Physics (IMP). The full-length sextupole coil is wound by a single Nb₃Sn round wire. And due to the complicated technology process and the stress sensitivity, this coil is indeed a great technical challenge. In order to test the performance of the individual sextupole coil, a sextupole magnetic mirror structure based on the bladder and key technology is utilized. This paper presents the mechanical design of the mirror structure along with fabrication details, the room temperature assembly, and the first test results, respectively.

I. Introduction

Afourth generation ECR ion source (FECR), which is one of the key components of Low Energy heavy ion Accelerator Facility (LEAF) at the Institute of Modern Physics, is under research and development to achieve the magnetic field required for operating at the microwave frequency of 45 GHz [1]. The FECR magnet support structure, is based on an aluminum shell surrounding the coils and iron yoke and pretensioned using water-pressurized bladders and interference keys. The all-Nb₃Sn superconducting coil system is based on the traditional sextupole-in-solenoid configuration, which consists of 6 identical sextupole coils, 2 injection solenoids, 1 middle solenoid and 1 extraction solenoid [2]–[4].