Improvement of microwave injection for heavy-ion production at a compact ECR ion source

A prototype compact electron cyclotron resonance ion source with all pemianent magnets named Kei3 and based on Kei2, has been developed to produce various ions. Kei3 has an outer diameter of 280 mm and a length of 1120 nun. The magnetic field is funned by the same permanent magnet as Kei2. We investigated the basic performance of the Kei3 source at a previous experiment. The maximum beam current of C4+, N5+, O-6+ and Ne7+ were 565 mu A, 185 mu A, 99 mu A and 50.5 mu A, respectively. In order to increase the beam current of heavy ions, such as argon, we modified the microwave injection. The rf shield m the plasma chamber was used as a tuner of microwaves. The rf shield was installed at the position of a mirror peak of the injection side, and it can be moved 30 mm to an upstream side from there. As a result, we found optimal position of the rf shield for the production of Ar ions.