Gyrotrons for high power millimeter wave generation

The gyrotron is a new type of microwave tube capable of producing high power output at millimeter wavelengths. Oscillator results have been described in recent Soviet publications. This paper describes work in progress at Varian Associates, Inc. to develop an amplifier of the gyroklystron type to deliver 200 kW cw at 28 GHz. Considerable progress has been made with amplifier stability to the point that amplifier gains of up to 40 dB have been measured in a pulsed experimental amplifier. Current effort is concerned with improving efficiency. A pulsed oscillator is also described which produced 248 kW peak power at 28 GHz with 34 percent efficiency. A cw oscillator is under construction. Areas for future R and D are discussed. These include gyro-TWT amplifiers with increased instantaneous bandwidth (5 to 10 percent) and operation at harmonics of the cyclotron frequency to reduce the magnetic field requirements