Performance Test of CW 300 GHz Gyrotron FU CW I

A 300 GHz CWgyrotron FU CWI has been developed and installed in the ResearchCenter for Development of Far-Infrared Region, University of Fukui as a power source of ahigh frequency material processing system. Its performance was tested and the maximumpower of 1.75 kW/ CWhas been attained at the beam voltage of 15 kVand the beam current of1A. The maximumwindow power efficiency of 15.5%has been obtained at the cathode voltageslightly lower than 15 kV. This gyrotron is designed to deliver a Gaussian beam after modeconversion from the oscillation mode TE22,8 in the cavity with a complex of an internalradiator and beam shaping mirrors. The detailed measurement with an infrared camera hasconfirmed that a Gaussian beam is radiated when the magnetic field strength Bc at the cavityis adjusted at a proper value. However, within a range of Bc, the output power is emerged intomultiple directions, which suggests simultaneous oscillation of competing cavity modes.