Permanent magnet focusing of multimegawatt klystron beams

Departing from the usual technique of focusing large high power klystron beams by means of electromagnets, 24 megawatt, five-cavity klystrons for the Stanford two-mile linear accelerator were successfully built and tested using permanent magnet focusing at the Sperry Gyroscope Company. This paper briefly describes the 24 megawatt tube based upon a Stanford University design and covers in detail the development of the permanent magnet and stray field shielding. Performance data are presented showing nearly identical tube operating characteristics using either electromagnetic or permanent magnet beam focusing.