Enhanced ECR ion source performance with an electron gun

Abstract

An electron gun for the advanced electron cyclotron resonance (AECR) source has been developed to increase the production of high charge state ions. The AECR source, which operates at 14 GHz, is being developed for the 88-in. cyclotron at Lawrence Berkeley Laboratory. The electron gun injects 10 to 150 eV electrons into the plasma chamber of the AECR. With the electron gun the AECR has produced at 10 kV extraction voltage 131 e μA of O7+, 13 e μA of O8+, 17 e μA of Ar14+, 2.2 e μA of Kr25+, 1 e μA of Xe31+, and 0.2 e μA of Bi38+. The AECR was also tested as a single stage source with a coating of SiO2 on the plasma chamber walls. This significantly improved its performance compared to no coating, but direct injection of electrons with the electron gun produced the best results.