An intense interaction coupled cavity output section

Summary form only given. A program has been underway at Varian to develop linear beam amplifiers that would provide relatively broadband performance in the pulse power range from 0.5 MW to 1.5 MW. Early efforts resulted in low efficiency. Peak efficiencies varied from 21% to 32% with band edge efficiencies from 15% to 23%. TWT theories have always called for an output circuit with over 20 db gain to provide efficiency. However, in a recent program it has been found that greatly improved efficiency may result from gain of only 6 to 10 db. Theoretical studies of beam-circuit interaction on the large signal computer program have shown that highly efficient operation could be achieved with a "short" output stack of cloverleaf cavities. When this short stack is adjusted in length for maximum efficiency, it provides only 6 to 10 db of small signal gain with predicted efficiencies as high as 65%. A short stack Twystron^® was built for the LMW level at C-band and it verified the theoretical studies. It provided 1.1 times the efficiency of the standard long stack tube. A short stack Twystron^® was designed for the 1 MW level at S-band and provided L5% peak efficiency where previous long stack efforts provided 25%. A short stack intense interaction cloverleaf output section in a newly developed TWT/EIK configuration has been shown to be theoretically advantageous. When the S-band short stack Twystron^® was configured this way, the measured efficiency was 51% and under one set of conditions was 59%^.