Theoretical research on TEM mode feedback for compact design of an X-band triaxial klystron amplifier

A relativistic triaxial klystron amplifier (TKA) is considered to be one of the most promising high power microwave (HPM) sources for coherent power combination in high frequency bands. In general investigations, the TEM mode leakage and asymmetric modes' competition are considered to play unfavorable roles in the normal operation of TKA. Therefore, mode reflectors with high reflection efficiency in both the TEM mode and the asymmetric modes are employed and expected to significantly suppress the transmissions of the microwaves between the cavities. So the cavities can be separated from each other, while the long drift length is necessary to achieve the deep modulation. Therefore, the size of TKA is noticeably larger compared to other HPM oscillators, which requires large magnetic coil and huge energy consumption. In our present research, it is found that the TEM mode leakage can be utilized to form positive feedback between the cavities, which is significant for electron beam modulation and furthermore t...