Optimization of Microwave Injection at Compact ECR Ion Source

A prototype compact ECR ion source, named Kei3, has been developed for the production of various ions. Kei3 consists of upstream vacuum chamber, permanent magnets and plasma chamber, and downstream vacuum chamber with extraction system. The magnetic field was copied from present prototype Kei2. As a result of basic beam tests of Kei3, the maximum beam currents of C⁴⁺, N⁵⁺, O⁶⁺ and Ne⁷⁺ were 565 μA, 185 μA, 99 μA, and 50.5 μA, respectively. In order to increase the beam current of heavy ions such as argon, we modified the microwave injection. Moreover, we tested two-frequency heating for increasing the current of highly charged argon. A maximum current of 60.4 μA for Ar⁷⁺ was obtained in plate position of 7 mm at longer waveguide. Second, we tested two-frequency heating technique for increase the highly charged argon ions. We could increase a beam intensity of Ar⁸⁺ from 9.7 to 15.4 μA.