A C-band gyro-TWT

The operating characteristics of a gyrotron travellng wave tube (gyro-TWT) operating at C-band are reported. Detailed testing showed that at higher beam voltage and current and with a magnetic field profile increasing in magnitude toward the rf output window, the output power could be increased from 50 kW at 16.6% efficiency to 128 kW at 24% efficiency. The maximum efficiency measured was 26% at 120 kW. Experimental data on small and large signal gain, bandwidth, output power and efficiency will be presented. The gyro-TWT employs a magnetron injection gun to provide an electron beam with a prescribed perpendicular to parellel velocity ratio. Inherent in this type of electron gun is a finite spread in the two velocity components. An alternate method for producing an electron beam with very low spread in the velocity components is presented. Design data will be presented.