Design and Optimization of Reflectors in a Relativistic Triaxial Klystron Amplifier

The inevitable power leakage of the TEM mode in relativistic triaxial klystron amplifier (TKA) devices will cause energy coupling between different beam-wave interaction cavities, which could interfere or even damage the stable operation of the devices. Specially designed mode reflectors have been proposed to suppress the power leakage of the TEM mode in TKA devices. The design and optimization methods of the reflectors have been investigated systematically in this article. The research results show that a reflector is essentially a high-order mode cavity, and the frequency of this mode is close to the operation frequency of the devices. Furthermore, the effects of reflector loading on the cavities are investigated and compound modulation of multiple cavities with reflectors is examined. The simulation results demonstrate that the loading of downstream cavities will aggravate the energy coupling between the upstream cavities. To achieve the isolation of cavities in multireflector devices, the eigenfrequencies of the two reflectors in front of the bunching cavities should be separated as far as possible. With the employment of three carefully designed reflectors, the power leakage of the TEM mode is controlled within an acceptable range and no parasitic frequency self-excitation is observed inside a proposed Ku-band TKA device.