Design of a RF interaction system for a Ka-band EIK

In this paper, a RF interaction system used in a Ka-band CW extended interaction klystron (EIK) is introduced. The circuit of this system is analyzed and optimized by using Computer Simulation Technology (CST). A sample tube has been fabricated in the summer of 2018. Working at frequency point 35. 07GHz, with the 8.2kV cathode voltage and the 0.36A cathode current, the tube reaches 440W CW output power, and its 3dB bandwidth is over 120MHz. By adjusting the curcuit of output cavity, Particle-in-Cell (PIC) simulation results show that the system is capable of achieving 27.6
^%
electronic efficiency at 35GHz, CW output power reaching about 1250W.