Study on the Efficiency of Klystrons

The limits of beam-to-radio frequency (RF) efficiency, which are achievable using klystrons, are discussed in this article. Interaction between the electron beam and RF field in the output cavity is also investigated. A 100% efficiency could be achieved for certain RF fields and point-like beams. However, efficiency is reduced when fringe field, space-charge effect, and transverse beam distribution are considered. Numerical calculations on these factors are presented to investigate the power extraction mechanism in the output cavity, which will help in the optimization of future klystron designs. Large-signal klystron simulation code KlyC is used for 1-D and 1.5-D calculations.