Development of a High Power Ka-Band Extended Interaction Klystron

After completing the designs of the electron gun with large compression ratio, the stable electron optics system with high transmission, and the efficient beam-wave interaction circuit, using a permanent magnetic uniform field focusing, we have successfully built a high power Ka-band extended interaction klystron with excellent performance. The working voltage and current are about 25.5 kV and 3.1 A, respectively. The measured DC beam transmission is over 97%, and in the most adverse state of high frequency operation, the transportation can still keep the value of over 90%. In the condition of non-equal excitation, the device demonstrates the bandwidth of 435 MHz corresponding to the output power of 10 kW or more. The duty cycle is over 3%. Near the optimal working point, the klystron clearly shows its potential, which means that the maximum output power exceeds 20 kW with The gain 44 dB and the efficiency 25% in the bandwidth of 60 MHz.