Abstract
Gyrotron Backward Wave Oscillator (Gyro-BWO) for its high power handling and wide frequency tuning capability is one of the promising high power coherence radiation sources. Physical processes in gyro-BWO are investigated with a numerical approach which evaluates the self-consistent field profile by employing outgoing-wave boundaries at the open ends. Changing the operating condition such as magnetic field strength or beam voltage could tune the oscillation frequency. Theoretically, the frequency tuning should be as smooth as the operating parameter gradually changed, according to the w-k diagram. However in the most of the gyro-BWO's experiment, instead of smooth tuning curve, it is frequent observed that the oscillation frequency is a zigzag curve. Frequency jumping commonly observed in the gyro-BWO during magnetic field and voltage tuning is experimentally characterized. Injection locking of a Ka-band Gyro-BWO which can control the oscillation frequency, phase and even output power operating in the TE11 mode resulted in an output power of 154kW and efficiency enhancement up to 38%. Various effects of injection locking observed in the experiment will be reported which suggest areas for further theoretical and experimental study.