Slotted Antenna Waveguide for Microwave Injection in Ion Sources

This paper presents the design of an innovative method of microwaves injection inside an Ion source plasma chamber based on slotted waveguide antennas. This microwave launching system placed along the side walls has advantages with respect to the conventional axial end-launch waveguide scheme, and its adoption could be relevant for improving the performances of Electron Cyclotron Resonance Ion Sources (ECRISs) [1]. A better power coupling and a more symmetric power distribution from the multiple radiating waveguide slots, has been obtained by the proposed design. The slotted waveguide, operating in the band [14.2;15.25] GHz exhibits a tuning range of about 7%, thanks to the launcher to cavity coupler optimization carried out with the commercial simulator CST Microwave Studio. The modal distribution coupled inside the plasma chamber by the new launching scheme has been compared with the one obtained by the classical axial launching scheme. Furthermore, a numerical validation of future electric field profile measurement through bead-pull has been performed.