Design and demonstration of a klystron with 62 percent efficiency

Extensive design optimization studies on a prototype series of klystrons have been carried out using a digital computer simulation, Five parameters were investigated for their effect on efficiency: 1) penultimate cavity tuning; 2) pre-penultimate cavity tuning; 3) beam perveance; 4) pre-pre-penultimate cavity tuning; and 5) output gap transit angle, These studies indicate that the power conversion efficiency of a high-power narrow-band multicavity klystron of optimum design should lie in the 70-80 percent range. A tube of near-optimum design was built and its performance was carefully measured as a function of two parameters: 1) penultimate and pre-penultimate cavity tuning; and 2) beam voltage. The measured data were used as a guide to determine the choice of beamfilling factor and beam power interception for best correlation with computed results. The measured efficiency was 62±1.5 percent compared to the computed value of 64 percent. Careful attention was paid to the repeatability of the efficiency measurements and to the effect of nonideal pulse shape on calorimetric measurements. Beam interception at large-signal levels appears to be the phenomenon which limits efficiency in the present tube.