Suppression of high order mode oscillation and parasitic RF output in 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. A new method to suppress the high order modes will be introduced in this paper. By putting selective absorbing material on coupling slot of the double-gap coupling cavity, all the high order modes with π mode field structure can be suppressed effectively. This method has been applied to C-band MBKs successfully.