Suppression of parasitic mode oscillation in relativistic klystron amplifier

The paper studies the higher order parasitic mode oscillation in input cavity and idler cavity of relativistic klystron amplifier(RKA). The parasitic mode in resonant cavity is proved to be TM11 mode, which is transformed into TE11 mode in drift tube. According to the transporting property of the parasitic mode in drift tube, the microwave attenuating material placed in the inner wall of drift tube is adopted to suppress the parasitic mode oscillation. The suppression of parasitic mode growth is also analyzed with microwave attenuating material of different conductivity and length. The three dimensional simulation of an RKA with attenuating material is carried out, and the results show that the introduction of proper microwave attenuating material can well suppress parasitic mode oscillati