Oscillation Characteristics of CW 300 GHz Gyrotron FU CWI

A CW 300 GHz gyrotron has been developed and installed in University of Fukui. A quasi-Gaussian beam is delivered through the vacuum window after mode conversion from the TE22.8 cavity mode with a complex of an internal radiator and beam shaping mirrors. Performance test has been carried out and the maximum CW output power of 1.75 kW has been attained at the beam voltage of 15 kV and the beam current of 1A. The maximum efficiency of 15.5% is obtained at the cathode voltage slightly lower than 15 kV.