Survey of recent gyrotron developments

Rapid progress has been made in improving the performance of gyromonotron oscillators and gyro-TWT amplifiers and in exploring new gyrotron configurations with specific advantageous features. A gyromonotron at 35 GHz and 340 kW has been operated with improved efficiency of 54%. Very large CW power of 214 kW has been achieved at 60 GHz, and pulsed power (0.1 ms) of 120 kW has been achieved at a frequency as high as 375 GHz. A gyro-TWT amplifier with useful bandwidth (∼ 2%) has been opoerated with peak power > 20 kW at 94 GHz. Several successful demonstrations have been made of gyrotrons operating at high harmonics of the electron cyclotron frequency with implications for greatly reduced magnetic field requirements. There has also been an initial demonstration of a gyro-BWO (at X-band) and encouraging gyro-BWO designs at 80-110 GHZ which promise broadly-tunable, high-power, millimeter-wave sources.