A review of studies for the variable frequency superconducting ECR ion source project at MSU

The SC-ECR ion source is now under construction at MSU. In this paper, studies undertaken in conjunction with this ion source project will be reviewed. The magnet design studies were expanded to include a high-mirror-ratio axial profile, and we have completed a review of the impact of this possible design change on the solenoid coil structure. Upcoming tests of the prototype solenoid coil structure will be described. Hexapole coils have been wound and successfully tested, and we will summarize those results. In order to establish a basis for selecting the axial field profile, the RT-ECR was modified to operate on a two mirror profile with a high mirror ratio on the first stage side, and the results of this study will be presented. A key component of that test was a simple, single transmitter feed for both stages that is under consideration for the high frequency injection structure for the SC-ECR. Several new ECR beam formation studies have been initiated. ERAY calculations suggest that the angular tilt of the puller electrode nose has an important effect on the extracted emittance. In another study, we properly measured the voltage dependence of the RT-ECR total extracted current, and can identify two regimes of operation. Recent emittance measurements on the RT-ECR will be discussed. We have also measured the energy spread of argon ions through 10+ and new aspects of these measurements will be reported, including: observation of higher energy low charge ions, a preliminary explanation of the gas mixing effect in ECR sources as an ion cooling process, and observation of an ion energy dependence on rf power