Plasma heating and innovative microwave launching in ECRIS: models and experiments

Microwave-to-plasma coupling in ECRIS has been based on the classic scheme of waveguide-to-cylindrical plasma cavity matching. Optimization has been often obtained by empirical adjustments leading to an oversimplified model, though obtaining satisfactory performances. In order to overcome the ECR-heating paradigm, on-purpose design of launchers' setup and adequate diagnostics are going to be developed at INFN. This paper describes three-dimensional numerical simulations and Radio Frequency (RF) measurements of wave propagation in the microwave-heated magnetized plasmas of ion sources. Moreover, driven by an increasing demand of high frequency ECR ion sources, innovative ideas for the geometry for both the plasma chamber and the related RF launching system—in a microwave absorption-oriented scenario—are presented. Finally, the design of optimized launchers enabling "single-pass" power deposition, not affected by cavity walls effects, are described.