RF waves and RF coupling systems in ECR ion sources

Despite the high level of performance today achieved, launching rf power in ECR ion sources (ECRIS) still remains very empirical, and the exact description of waves absorbed in ECRIS is also a major unknown. The present article simply tries to give some answer to the following questions: which rf wave has to be launched, and how to launch this wave in order to efficiently heat the plasma electrons and optimize the rf power absorption as well as the source performance? Therefore two main aspects of this problem are considered: (i) on one hand the rf waves that can exist and propagate in ECRIS, either plasma waves or electromagnetic eigenmodes, (ii) on the other hand the rf coupling systems to develop accordingly. Emphasis is given to the latter topics. (author)