Experiments with high-power CW klystrons using extended interaction catchers

This paper reports results on a two-year research program, most of which has already been presented orally. The objective was to exploit the extended interaction principle to obtain more CW power output, bandwith, and efficiency than a classical klystron would give. An attempt is made to arrive at criteria for comparing classical klystron catchers with extended interaction catchers and possibily with traveling-wave amplifiers. Results of tests on various experimental tubes are given and discussed. It is pointed out that the improvement in performance varies as the amount of extension of the catcher but this is limited by self-oscillation. Agreement between experimental results and a start oscillation theory developed for the structure tested is fairly good. It is concluded that the most likely application is in high average power tubes at very high frequencies, X band and higher; and that further research is needed on slow-wave circuits and on extended bunchers.