The research on parasitic RF output of Multi-Beam Klystrons

The high order mode oscillation and parasitic RF output have serious influence on the normal operation and the purity of the output spectrum of MBKs. By putting a microwave absorbing block in the coupling slot of the double-gap coupling cavity, all the high order modes with π mode field structure can be suppressed effectively. The experiment indicated that the size and shape of the absorbing block have big influence on the stability of the MBK. The influence of the absorbing block on the properties of the modes in double gap coupling cavity (DGCC) is calculated and analyzed in this paper. By using PIC code, the beam-wave interaction in DGCC is also calculated. Based on above calculations, it is possible to determine the suitable size and shape of absorbing block while keeping the MBKs operate stable on the high power level.