Rigorous evaluation of the performance of output cavities in high efficiency klystron amplifiers

The rigorous, 3-D, nonlaminar electron trajectory program which was reported at the 1971 IEEE-ED Conference was applied to a large number of high efficiency klystron designs and the results compared with both, experimental results and presently existing one-dimensional and otherwise less rigorous programs available at industrial klystron laboratories. The conclusions from the evaluation can be summarized as follows: the most important difference between the results of the rigorous program and other programs is that the former predicts efficiencies to be 10 to 15 percentage points smaller than the latter, in excellent agreement with measured klystron efficiencies at efficiency levels above 50%. Another important difference is the accurate prediction of the fact that η has a maximum at finite values of the output gap angle θ and not at θ → 0. Interception is predicted accurately and, for a given set of design parameters, the efficiencies agree, within ± 1%, with measured values. In addition, 3-D velocities at the output are available.