Quasi-optical mode converter for 1MW dual-frequency gyrotrons

A quasi-optical (q.o.) mode converter has been designed for the MW-level dual-frequency gyrotron which is under development for the upgrade of the electron cyclotron (EC) system of the TCV tokamak. The gyrotron design is essentially based on modifications of the W7-X gyrotron [1]. The launcher of the output coupler has been synthesized to adapt the geometry of the quasi-elliptical mirror with same size as in the W7-X gyrotron for both operating modes (TE17,5 @ 85GHz, TE26,7 @ 126GHz). The simulation results show that high conversion efficiencies and low stray radiations in the q.o. system can be achieved.