Some physical phenomena in the collector region of multi-beam klystron

Some physical phenomena had been observed in the collector region of the C-band and S-band MBKs made by Institute of Electronics, Chinese Academy of Sciences (IECAS). One of them is the overheating of the collector inner surface, which will lead to the evaporation of the copper. The second one is the potential drop at the entrance of the collector, which will lead to the electron reflection. The third one is the microwave leakage at the collector ceramic insulator. These phenomena will be described in this paper. The calculation results on the spread of multiple electron beams and the resonant modes in the collector region were also given. Some suggestions for solving these problems will be discussed.