Millimeter wave, 25 kW CW gyrotrons using permanent-magnets

Summary form only given. Two compact 25 kW CW, low magnetic field gyrotrons have been designed for use in Ka-Band and W-Band systems. Both 50 kV devices have been designed to minimize their size and weight by using a 4.5 kG Samarium Cobalt permanent magnet. Their designs are presented. The 35 GHz gyrotron uses a 3 A MIG and operates at the third harmonic in the TE/sub 411/ mode of a smooth-bore cylindrical cavity. For an output power of 25 kW, the predicted conversion efficiency is 25%, yielding an output efficiency of 17%. An ideal 33 kV single-stage depressed collector following a magnetic downtaper could increase the device efficiency to 50%. The 94 GHz gyrotron utilizes a Cusp gun and operates at the eighth-harmonic in a sixteen-vane slotted cavity. The efficiency of the 95 GHz gyrotron is predicted to be 10%, which could also be boosted to /spl sim/50% with a depressed collector. Either device can be reconfigured as a tunable gyro-BWO. Mode competition is controlled in both gyrotrons by slicing the cavities to interrupt the azimuthal wall currents of unwanted modes as utilized recently in our successful second-harmonic TE/sub 21/ gyro-TWT amplifier experiment.